Vaxcyte (PCVX) 10-K 27 Feb 24 2023 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2023	Feb. 23, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Trading Symbol	PCVX
Entity Registrant Name	VAXCYTE, INC.
Entity Central Index Key	0001649094
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity File Number	001-39323
Entity Tax Identification Number	46-4233385
Entity Address, Address Line One	825 Industrial Road
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	San Carlos
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94070
City Area Code	650
Local Phone Number	837-0111
Entity Common Stock, Shares Outstanding		108,407,730
Entity Public Float			$ 4.1
Document Annual Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE
Title of 12(b) Security	Common Stock, $0.001 par value per share
Security Exchange Name	NASDAQ
Documents Incorporated by Reference	Part III of this Annual Report on Form 10-K incorporates information by reference from the Registrant’s definitive proxy statement to be filed with the U.S. Securities and Exchange Commission pursuant to Regulation 14A, not later than 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K, in connection with the Registrant’s 2024 annual meeting of stockholders.
Auditor Name	Deloitte & Touche LLP
Auditor Location	San Francisco, California
Auditor Firm ID	34
Document Financial Statement Error Correction [Flag]	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 397,451	$ 834,657
Short-term investments	682,776	96,719
Prepaid expenses and other current assets	15,727	11,179
Total current assets	1,095,954	942,555
Property and equipment, net	79,626	10,360
Operating lease right-of-use assets	30,997	21,288
Long-term investments	162,675	26,549
Restricted cash	1,103	871
Other assets	37,562	4,555
Total noncurrent assets	311,963	63,623
Total assets	1,407,917	1,006,178
Current liabilities:
Accounts payable	14,587	9,795
Accrued compensation	11,056	1,180
Accrued manufacturing expenses	52,767	8,265
Accrued expenses	59,815	15,375
Operating lease liabilities - current	7,113	5,910
Total current liabilities	145,338	40,525
Operating lease liabilities - long-term	22,111	12,031
Other liabilities	0	9
Total liabilities	167,449	52,565
Commitments and contingencies (Note 7)
Stockholders' Equity
Preferred stock, $0.001 par value - 10,000,000 authorized at December 31, 2023 and December 31, 2022; no shares issued and outstanding at December 31, 2023 and December 31, 2022	0	0
Common stock, $0.001 par value - 500,000,000 shares authorized at December 31, 2023 and December 31, 2022; 95,364,831 and 79,470,670 shares issued and outstanding at December 31, 2023 and December 31, 2022, respectively	98	82
Additional paid-in capital	2,164,583	1,476,018
Accumulated other comprehensive income (loss)	179	(361)
Accumulated deficit	(924,392)	(522,126)
Total stockholders' equity	1,240,468	953,613
Total liabilities and stockholders' equity	$ 1,407,917	$ 1,006,178

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	95,364,831	79,470,670
Common stock, shares outstanding	95,364,831	79,470,670

Statements of Operations

Statements of Operations - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating expenses:
Research and development (including related party expenses of $0, $0 and $2,359 in 2023, 2022 and 2021, respectively)		$ 332,341	$ 169,451	$ 78,411
Acquired manufacturing rights (Note 7)		75,000	22,995	0
General and administrative		60,700	39,810	25,259
Total operating expenses		468,041	232,256	103,670
Loss from operations		(468,041)	(232,256)	(103,670)
Other income (expense), net:
Interest expense		0	(2)	(7)
Interest income		62,907	8,356	344
Grant income		4,765	1,931	1,585
Realized gains on marketable securities		0	0	2
Loss on disposal of fixed assets		0	(44)	0
Foreign currency transaction (losses) gains		(1,897)	(1,470)	1,669
Total other income, net		65,775	8,771	3,593
Net loss		$ (402,266)	$ (223,485)	$ (100,077)
Net loss per share, basic		$ (4.14)	$ (3.44)	$ (1.93)
Net loss per share, diluted		$ (4.14)	$ (3.44)	$ (1.93)
Weighted-average shares outstanding, basic	[1]	97,157,690	64,877,988	51,922,108
Weighted-average shares outstanding, diluted	[1]	97,157,690	64,877,988	51,922,108
[1] Includes shares of common stock into which pre-funded warrants may be exercised. See Note 9, “Pre-Funded Warrants.”

Statements of Operations (Paren

Statements of Operations (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Research and development expense to related party	$ 0	$ 0	$ 2,359

Statements of Comprehensive Los

Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ (402,266)	$ (223,485)	$ (100,077)
Other comprehensive loss:
Unrealized gains (losses) on investments	538	(120)	(241)
Foreign currency translation adjustments, net	2	0	0
Comprehensive Loss	$ (401,726)	$ (223,605)	$ (100,318)

Statements of Redeemable Conver

Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity - USD ($) $ in Thousands	Total	At The Market Offering	Follow On Public Offering	Sutro Stock Payment	Common Stock	Common Stock At The Market Offering	Common Stock Follow On Public Offering	Common Stock Sutro Stock Payment	Additional Paid-in Capital	Additional Paid-in Capital At The Market Offering	Additional Paid-in Capital Follow On Public Offering	Additional Paid-in Capital Sutro Stock Payment	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2020	$ 345,843				$ 54				$ 544,353				$ (198,564)
Beginning balance, shares at Dec. 31, 2020					51,071,593
Issuance of common stock upon initial public offering or at-the-market offering, net of issuance costs		$ 13,847				$ 1				$ 13,846
Common stock shares sold						567,045
Issuance of common stock under Employee Stock Purchase Plan	888								888
Issuance of common stock under Employee Stock Purchase Plan (in shares)					62,546
Release of restricted stock units	0
Exercise of stock options	3,012								3,012
Exercise of stock options (in shares)					931,114
Issuance of common stock to LonzaLtd.	10,001				$ 1				10,000
Issuance of common stock to Lonza Ltd. (in shares)					399,680
Unrealized losses on investment	(241)													$ (241)
Vesting of early exercised stock options	16								16
Stock-based compensation expense	10,729								10,729
Cumulative translation adjustment	0
Net Income (Loss)	(100,077)												(100,077)
Ending balance at Dec. 31, 2021	284,018				$ 56				582,844				(298,641)	(241)
Ending balance, shares at Dec. 31, 2021					53,031,978
Issuance of common stock upon initial public offering or at-the-market offering, net of issuance costs		97,299	$ 759,181	$ 7,995		$ 4	$ 21			97,295	$ 759,160	$ 7,995
Common stock shares sold						3,921,528	21,062,500	167,780
Issuance of common stock under Employee Stock Purchase Plan	1,033								1,033
Issuance of common stock under Employee Stock Purchase Plan (in shares)					61,709
Release of restricted stock units	(861)								(861)
Release of restricted stock units, shares					46,603
Exercise of stock options	4,895				$ 1				4,894
Exercise of stock options (in shares)					1,178,572
Unrealized losses on investment	(120)													(120)
Vesting of early exercised stock options	8								8
Stock-based compensation expense	23,650								23,650
Cumulative translation adjustment	0
Net Income (Loss)	(223,485)												(223,485)
Ending balance at Dec. 31, 2022	953,613				$ 82				1,476,018				(522,126)	(361)
Ending balance, shares at Dec. 31, 2022					79,470,670
Issuance of common stock upon initial public offering or at-the-market offering, net of issuance costs		$ 90,741	$ 545,302			$ 2	$ 13			$ 90,739	$ 545,289
Common stock shares sold						2,095,943	13,030,000
Issuance of common stock under Employee Stock Purchase Plan	2,038								2,038
Issuance of common stock under Employee Stock Purchase Plan (in shares)					76,275
Release of restricted stock units	(3,876)								(3,876)
Release of restricted stock units, shares					154,135
Exercise of stock options	5,608				$ 1				5,607
Exercise of stock options (in shares)					537,808
Unrealized losses on investment	538													538
Vesting of early exercised stock options	8								8
Stock-based compensation expense	48,760								48,760
Cumulative translation adjustment	2													2
Net Income (Loss)	(402,266)												(402,266)
Ending balance at Dec. 31, 2023	$ 1,240,468				$ 98				$ 2,164,583				$ (924,392)	$ 179
Ending balance, shares at Dec. 31, 2023					95,364,831

Statements of Redeemable Conv_2

Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Parenthetical) - Common Stock - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Market offering
Issuance costs	$ 2,237	$ 3,107	$ 479
Follow On Public Offering
Issuance costs	$ 29,952	$ 45,814

Statements of Cash Flows (Unaud

Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net loss	$ (402,266)	$ (223,485)	$ (100,077)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,156	2,577	1,800
Stock-based compensation expense	48,760	23,650	10,729
Non-cash payments for acquired manufacturing rights	0	7,995	0
Loss on disposal of assets	0	44	97
Asset impairment charges	0	213	0
Amortization of operating right-of-use assets	7,015	6,619	1,657
Net amortization (accretion) of premium (discounts) on investments	(34,775)	(947)	1,406
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	17,870	433	(7,369)
Operating lease right-of-use assets	(16,724)	0	0
Other assets	(33,007)	(465)	(3,539)
Operating lease liabilities	11,284	1,151	(12,856)
Accounts payable	11,225	2,896	(12,470)
Accrued compensation	9,876	(2,275)	3,170
Accrued manufacturing expenses	44,501	3,826	(8,572)
Accrued expenses	36,295	7,171	4,631
Net cash used in operating activities	(296,790)	(170,597)	(121,393)
Cash flows from investing activities:
Purchases of property and equipment	(16,062)	(5,848)	(6,555)
Purchases of investments	(1,329,896)	(102,745)	(336,341)
Manufacturing facility and equipment construction-in-progress	(51,815)	0	0
Maturities of investments	611,876	168,691	100,500
Sales of investments	12,586	14,480	30,062
Proceeds from sales of property and equipment	0	7	26
Net cash (used in) provided by investing activities	(773,311)	74,585	(212,308)
Cash flows from financing activities:
Proceeds from issuance of common stock and pre-funded warrants from follow-on offerings, net of issuance costs	545,302	759,181	0
Proceeds from issuance of common stock under ATM Sales Program, net of issuance costs	90,741	97,299	13,896
Proceeds from exercise of common stock options	5,608	4,895	3,012
Proceeds from issuance of common stock under Employee Stock Purchase Plan	2,038	1,033	888
Release of restricted stock units	(3,876)	(861)	0
Net cash provided by financing activities	639,813	861,547	17,796
Effect of exchange rate changes on cash and cash equivalents	(6,686)	137	(439)
Net (decrease) increase in cash, cash equivalents and restricted cash	(436,974)	765,672	(316,344)
Cash, cash equivalents and restricted cash, beginning of period	835,528	69,856	386,200
Cash, cash equivalents and restricted cash, end of period	398,554	835,528	69,856
Supplemental disclosure of cash flow information:
Cash paid for interest	0	2	7
Supplemental disclosures of non-cash investing and financing activities:
Purchases of property and equipment recorded in accounts payable and accrued expenses	8,510	110	766
Issuance of common stock for acquired manufacturing rights	0	7,995	0
Stock issued for payment of accounts payable	$ 0	$ 0	$ 10,000

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ (402,266)	$ (223,485)	$ (100,077)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Dec. 31, 2023 shares
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	The adoption or termination of contracts, instructions or written plans for the purchase or sale of our securities by our Section 16 officers or directors for the three months ended December 31, 2023, of which was entered into during an open trading window and is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act (“10b5-1 Plan”), were as follows: Elvia Cowan , our Senior Vice President of Finance and Principal Accounting Officer , adopted a 10b5-1 Plan on November 13, 2023 . Ms. Cowan’s 10b5-1 Plan provides for the potential exercise and sale of up to 26,678 shares of our common stock, and expires on February 28, 2025 , or upon the earlier completion of all authorized transactions thereunder.
Name	Elvia Cowan
Title	Senior Vice President of Finance and Principal Accounting Officer
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	November 13, 2023
Termination Date	February 28, 2025
Arrangement Duration	1 year 3 months 15 days
Aggregate Available	26,678

Company Organization and Nature

Company Organization and Nature of Business	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Company Organization and Nature of Business	1. Company Organization and Nature of Business Vaxcyte, Inc. and its wholly owned consolidated subsidiary, collectively referred to as any of “we,” “us,” “the Company,” or “Vaxcyte,” headquartered in San Carlos, California, was incorporated in the state of Delaware on November 27, 2013 as SutroVax, Inc. and we changed our name to Vaxcyte, Inc. on May 15, 2020. On October 25, 2023, we formed Vaxcyte Switzerland GmbH (“Vaxcyte GmbH”), a wholly owned Swiss subsidiary. We are a clinical-stage vaccine innovation company engineering high-fidelity vaccines to protect humankind from the consequences of bacterial diseases. We are developing broad-spectrum conjugate and novel protein vaccines to prevent or treat bacterial infectious diseases. We are re-engineering the way highly complex vaccines are made through modern synthetic techniques, including advanced chemistry and the XpressCF cell-free protein synthesis platform, exclusively licensed from Sutro Biopharma, Inc. (“Sutro Biopharma”). Unlike conventional cell-based approaches, our system for producing difficult-to-make proteins and antigens is intended to accelerate our ability to efficiently create and deliver high-fidelity vaccines with enhanced immunological benefits. Our primary activities since incorporation have been to perform research and development, undertake preclinical and clinical studies and conduct manufacturing activities in support of our product development efforts; organize and staff our Company; establish our intellectual property portfolio; and raise capital to support and expand such activities.

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	2. Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation These consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (the “SEC”) regarding annual reporting. The consolidated financial statements include the Company and its wholly owned subsidiary. All intercompany transactions and balances have been eliminated upon consolidation. Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and expenses and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements. On an ongoing basis, we evaluate our estimates and assumptions, including those related to stock-based compensation expense, accruals for certain research and development costs, the incremental borrowing rate, the valuation of deferred tax assets and income taxes. Management bases our estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ materially from those estimates. Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that potentially subject us to a concentration of credit risk consist primarily of cash, cash equivalents and investments. We invest in money market funds, U.S. Treasury securities, U.S. government agency securities, corporate debt, commercial paper and asset-backed securities. We maintain bank deposits in federally insured financial institutions and these deposits may exceed federally insured limits. We are exposed to credit risk in the event of a default by the financial institutions holding our cash and issuers of investments to the extent recorded on the consolidated balance sheets. For example, on March 10, 2023, the California Department of Financial Protection and Innovation took control of Silicon Valley Bank (“SVB”) and appointed the Federal Deposit Insurance Corporation (“FDIC”) as receiver. While SVB was our primary bank at the time, we maintained banking relationships with other major banks. The substantial majority of funds we held at SVB, which included cash, cash equivalents and investments, were held in custodial accounts of a third-party institution for which SVB Asset Management was the advisor (“SVB Custodial Accounts”). On March 12, 2023, the FDIC confirmed that depositors of SVB would have access to all of their money and, as a result, we regained access to all of our funds deposited with SVB. The FDIC subsequently transferred SVB’s deposits and loans to a newly created bridge bank, named Silicon Valley Bridge Bank, N.A. (“Silicon Valley Bridge Bank”). On March 26, 2023, the FDIC announced that First Citizens Bank & Trust Company (“First Citizens Bank”) had agreed to purchase and assume all deposits and loans of Silicon Valley Bridge Bank. We have not experienced any losses on these deposits or investments as a result of this market event. While we were able to recover all deposited amounts from SVB, and continue to have access to all investments held in the SVB Custodial Accounts, there can be no assurance that our current or future banks will not face similar risks as SVB or that we will be able to recover in full our deposits in the event of similar closures. Our investment policy limits investments to money market funds, certain types of debt securities issued by the U.S. Government and its agencies, corporate debt, commercial paper and asset-backed securities, and places restrictions on the credit ratings, maturities and concentration by type and issuer. We have not experienced any significant losses on our deposits of cash, cash equivalents or investments. We are subject to supplier concentration risk from certain vendors. Although we are working to establish secondary sources of supply, we currently source several of our critical raw materials from single-source suppliers. We also use one contract manufacturing organization (“CMO”), Lonza Ltd. (“Lonza”), to handle most of our manufacturing activities for our VAX-24 and VAX-31 programs. If we were to experience disruptions in raw materials supplied by our suppliers, or in manufacturing activities at Lonza, we may experience significant delays in our product development timelines and may incur substantial costs to secure alternative sources of raw materials or manufacturing. Our future results of operations involve a number of other risks and uncertainties. Factors that could affect our future operating results and cause actual results to vary materially from expectations include, but are not limited to: our early stages of clinical vaccine development; our ability to advance vaccine candidates into, and successfully complete, clinical trials on the timelines we project; our ability to adequately demonstrate sufficient safety and immunogenicity or efficacy of our vaccine candidates; our ability to enroll subjects in our ongoing and future clinical trials; our ability to successfully manufacture and supply our vaccine candidates for clinical trials or for future potential commercialization; our ability to obtain additional capital to finance our operations; our ability to obtain, maintain and protect our intellectual proper ty rights; developments relating to our competitors and our industry, including competing vaccine candidates; general and market conditions; and other risks and uncertainties, including those more fully described in the “Risk Factors” section of this Annual Report on Form 10-K. Segment and Geographical Information We operate and manage our business as one reportable and operating segment. Our chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. Most of our long-lived assets are based in the United States. Long-lived assets are comprised of property and equipment. Cash, Cash Equivalents and Restricted Cash We consider all highly liquid investments purchased with original maturities of three months or less from the date of purchase to be cash equivalents. Cash equivalents consist primarily of amounts invested in money market funds and commercial paper and are stated at their fair values. Restricted cash consists of two standby letters of credit that serve as collateral for the lease agreements for our current corporate headquarters. Cash, cash equivalents and restricted cash as reported within the consolidated statements of cash flows consisted of the following: Years Ended December 31, 2023 2022 (in thousands) Cash and cash equivalents $ 397,451 $ 834,657 Restricted cash 1,103 871 Cash, cash equivalents and restricted cash $ 398,554 $ 835,528 Investments Our investments have been classified and accounted for as available-for-sale securities. Fixed income securities consist of U.S. Treasury securities, U.S. government agency securities, corporate debt, commercial paper and asset-backed securities. These securities are recorded on the consolidated balance sheets at fair value. Unrealized gains and losses on these securities are included as a separate component of accumulated other comprehensive gain (loss). The cost of investment securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in other income (expense), net. Realized gains and losses are also included in other income (expense), net. When the fair value of a debt security declines below its amortized cost basis, any portion of that decline attributable to credit losses, to the extent expected to be nonrecoverable before the sale of the security, is recognized in our consolidated statements of operations. When the fair value of a debt security declines below its amortized cost basis due to changes in interest rates, such amounts are recorded in other comprehensive loss, and are recognized in our consolidated statements of operations only if we sell or intend to sell the security before recovery of its cost basis. Property and Equipment, Net Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally three to five years . Leasehold improvements are amortized over the shorter of the expected life or lease term. Repairs and maintenance expenditures, which are not considered improvements and do not extend the useful life of property and equipment, are expensed as incurred. When assets are retired or otherwise disposed of, the cost and related accumulated depreciation and amortization are removed from the consolidated balance sheets and the resulting gain or loss is reflected in the consolidated statements of operations in the period realized. Leases We determine if an arrangement is a lease at inception. In addition, we determine whether a lease meets the classification criteria of a finance or operating lease at the lease commencement date considering whether: (i) the lease transfers ownership of the underlying asset to the lessee at the end of the lease term; (ii) the lease grants the lessee an option to purchase the underlying asset that the lessee is reasonably certain to exercise; (iii) the lease term is for a major part of the remaining economic life of the underlying asset; (iv) the present value of the sum of the lease payments and residual value guaranteed by the lessee equals or exceeds substantially all of the fair value of the underlying asset; and (v) the underlying asset is such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease term. As of December 31, 2023 and 2022, our lease population consisted of real estate operating leases and we did no t have any finance leases. Operating leases are included in Operating lease right-of-use (“ROU”) assets, Operating lease liabilities — current and Operating lease liabilities — long term in our consolidated balance sheets. ROU assets represent our right to use the underlying assets for the lease term and lease liabilities represent our obligation to make lease payments arising from the leases. Operating lease ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the present value of lease payments, if the rate implicit in the lease is not readily determinable, we use our incremental borrowing rate based on the information available at the lease commencement date. We determine the incremental borrowing rate based on an analysis of corporate bond yields with a credit rating similar to ours. The determination of our incremental borrowing rate requires management judgment, including development of a synthetic credit rating and cost of debt, as we currently do not carry any debt. We believe that the estimates used in determining the incremental borrowing rate are reasonable based upon current facts and circumstances. Applying different judgment to the same facts and circumstances could yield a different incremental borrowing rate. The operating lease ROU assets also include adjustments for prepayments and accrued lease payments and exclude lease incentives. ROU assets and lease liabilities may include options to extend or terminate leases if it is reasonably certain that we will exercise such options. Lease payments which are fixed and determinable are amortized as rent expense on a straight-line basis over the expected lease term. Variable lease costs, which are dependent on usage, a rate or index, including common area maintenance charges, are expensed as incurred. Lease agreements that include lease and non-lease components are accounted for as a single lease component. Lease agreements with non-cancelable terms of less than 12 months are not recorded on our consolidated balance sheets. Impairment of Long-Lived Assets We review long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparing the carrying amount to the future undiscounted net cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recogni zed is measured as the amount by which the carrying amount of the assets exceeds the projected discounted future net cash flows generated by the assets. There were $ 0 million, $ 0.2 and $ 0 million of impairments of long-lived assets during the years ended December 31, 2023 , 2022 and 2021, respectively. Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. The carrying amounts of our financial instruments, including cash and cash equivalents, prepaid and other current assets, accounts payable, accrued expenses, and other liabilities, approximate fair value due to their short-term maturities. Research and Development Research and development costs are expensed as incurred. Research and development costs include salaries, stock-based compensation and benefits for employees performing research and development activities, an allocation of facility and overhead expenses, expenses incurred under agreements with consultants, CMOs, contract research organizations (“CROs”) and investigative sites that conduct preclinical studies, clinical trials other supplies and costs associated with product development efforts, preclinical activities, clinical trials and regulatory operations. Accrued Research and Development We have entered into various agreements with CROs and CMOs. Our research and development accruals, which include accrued manufacturing expenses, are estimated based on the level of services performed, progress of the studies, including the phase or completion of events, and contracted costs. The estimated costs of research and development services provided, but not yet invoiced, are included in accrued expenses on the consolidated balance sheets. If the actual timing of the performance of services or the level of effort varies from the original estimates, we adjust the accrual accordingly. Payments made to CROs or CMOs under these arrangements in advance of the performance of the related services are recorded as prepaid expenses and other current assets until the services are rendered. To date, there have been no material differences between our estimates of such expenses and the amounts actually incurred. Acquired Manufacturing Rights In December 2022, we entered into an option agreement with Sutro Biopharma (the “Option Agreement”). The Option Agreement we acquired, among other things, a right, but not an obligation, to obtain certain exclusive rights to internally manufacture and/or source extract from certain CMOs and the right to independently develop and make improvements to the extract for use in connection with the exploitation of certain vaccine compositions (the “Option”). As consideration for the Option and other rights and authorizations granted to us under the Option Agreement, we paid Sutro Biopharma upfront consideration. In September 2023, we and Sutro Biopharma mutually agreed in writing to the Form Definitive Agreement (as defined below) to become effective in the event we exercised the Option, and paid Sutro Biopharma the amount due upon mutual agreement of the Form Definitive Agreement. In November 2023, we exercised the Option and paid the Option exercise price and accrued the remaining payment we are obligated to pay Sutro Biopharma. As of December 31, 2022 and 2023, we have determined there is no current alternative future use of the acquired manufacturing rights paid and expensed the Option as of December 31, 2022 and 2023. We have classified such costs incurred related to the execution of the Option Agreement, the mutual agreement of the Form Definitive Agreement and the Option exercise, as Acquired Manufacturing Rights on the accompanying consolidated statements of operations for the years ended December 31, 2022 and 2023, respectively. See Note 7, “Commitments and Contingencies, Sutro Option Agreement,” for further details. Income Taxes We account for income taxes using the asset and liability method. We recognize deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the consolidated financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the consolidated financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. In evaluating the ability to recover our deferred income tax assets, we consider all available positive and negative evidence, including our operating results, ongoing tax planning and forecasts of future taxable income on a jurisdiction-by-jurisdiction basis. In the event we determine that we would be able to realize our deferred income tax assets in the future in excess of their net recorded amount, we would make an adjustment to the valuation allowance that would reduce the provision for income taxes. Conversely, in the event that all or part of the net deferred tax assets are determined not to be realizable in the future, an adjustment to the valuation allowance would be charged to earnings in the period when such determination is made. As of December 31, 2023 and 2022, we have recorded a full valuation allowance on our deferred tax assets. Tax benefits related to uncertain tax positions are recognized when it is more likely than not that a tax position will be sustained during an audit. Interest and penalties related to unrecognized tax benefits are included within the provision for income tax. Stock-Based Compensation Expense For options granted to employees, non-employees and directors, stock-based compensation is measured at grant date based on the fair value of the award. We determine the grant-date fair value of the options using the Black-Scholes option-pricing model. The fair value of restricted stock and restricted stock unit (“RSU”) awards is determined based on the number of units granted and the closing price of the Company’s common stock as of the grant-date. The grant-date fair value of awards is amortized over the employees’ requisite service period or the non-employees’ vesting period as the services are rendered. Forfeitures are accounted for as they occur. Additionally, our 2020 Employee Stock Purchase Plan is deemed to be a compensatory plan and is therefore included in stock-based compensation expense. Comprehensive Loss Comprehensive loss includes net loss and other comprehensive loss for the period. Other comprehensive loss consists of unrealized loss on investments and foreign currency translation adjustments, net. Foreign Currency Transactions Transactions denominated in foreign currencies are initially measured in U.S. dollars using the exchange rate on the date of the transaction. Foreign currency denominated monetary assets and liabilities are subsequently re-measured at the end of each reporting period using the exchange rate at that date, with the corresponding foreign currency transaction gain or loss recorded in the consolidated statements of operations and consolidated statements of cash flows. Nonmonetary assets and liabilities are not subsequently re-measured. For our international operations, local currencies have been determined to be the functional currencies. We translate functional currency assets and liabilities to their U.S. dollar equivalents at exchange rates in effect as of the balance sheet date and income and expense amounts at average exchange rates for the period. Gains and losses from foreign currency translation are included in accumulated other comprehensive loss within stockholders’ equity in the consolidated balance sheets. Net Loss Per Share Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common stock outstanding, including pre-funded warrants, during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, common stock subject to repurchase, and stock options are considered to be potentially dilutive securities. Shares of common stock into which the pre-funded warrants may be exercised are considered outstanding for the purposes of computing net loss per share because the shares may be issued for little consideration, are fully vested and are exercisable after the original issuance date. Basic and diluted net loss attributable to common stockholders per share is presented in conformity with the two-class method required for participating securities as the redeemable convertible preferred stock is considered a participating security. Our participating securities do not have a contractual obligation to share in our losses. As such, the net loss was attributed entirely to common stockholders. Because we have reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods. Recently Issued Accounting Standards Not Yet Adopted From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies and adopted by us as of the specified effective date. We believe that the impact of recently issued standards that are not yet effective will not have a material impact on our consolidated financial statements and disclosures. In November 2023, the FASB issued Accounting Standards Update (“ASU”) No. 2023-07: Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. The ASU requires entities to report incremental information about significant segment expenses included in a segment’s profit or loss measure as well as the name and title of the chief operating decision maker. The guidance also requires interim disclosures related to reportable segment profit or loss and assets that had previously only been disclosed annually. This guidance is effective for annual periods beginning after December 15, 2024. We are currently evaluating the impact of the new guidance on the disclosures to our consolidated financial statements. In December 2023, the FASB issued ASU No. 2023-09: Income Taxes (Topic 740): Improvements to Income Tax Disclosures. The ASU improves the transparency of income tax disclosures by requiring (i) consistent categories and greater disaggregation of information in the rate reconciliation and (ii) income taxes paid disaggregated by jurisdiction. This guidance is effective for fiscal years beginning after December 15, 2024 on a prospective basis and retrospective application is permitted. We are currently evaluating the impact of the new guidance on the disclosures to our consolidated financial statements.

Fair Value Measurements and Fai

Fair Value Measurements and Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements and Fair Value of Financial Instruments	3. Fair Value Measurements and Fair Value of Financial Instruments Assets and liabilities recorded at fair value on a recurring basis in the consolidated balance sheets, as well as assets and liabilities measured at fair value on a non-recurring basis or disclosed at fair value, are categorized based upon the level of judgment associated with inputs used to measure their fair values. The accounting guidance for fair value provides a framework for measuring fair value and requires certain disclosures about how fair value is determined. Fair value is defined as the price that would be received upon the sale of an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The accounting guidance also establishes a three-level valuation hierarchy that prioritizes the inputs to valuation techniques used to measure fair value based upon whether such inputs are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect market assumptions made by the reporting entity. The three-level hierarchy for the inputs to valuation techniques is briefly summarized as follows: Level 1— Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; Level 2— Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level 3 — Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. Changes in the ability to observe valuation inputs may result in a reclassification of levels of certain securities within the fair value hierarchy. We recognize transfers into and out of levels within the fair value hierarchy in the period in which the actual event or change in circumstances that caused the transfer occurs. Level 1 securities consist of highly liquid money market funds for which the carrying amounts approximate their fair values due to their short maturities. U.S. Treasury securities are valued using Level 1 inputs based on unadjusted, quoted prices in active markets that are observable at the measurement date for identical assets or liabilities. Level 2 securities, consisting of corporate debt, commercial paper, U.S. government agency securities and asset-backed securities, are measured based on other observable inputs, including broker or dealer quotations or alternative pricing sources. When quoted prices in active markets for identical assets or liabilities are not available, we rely on non-binding quotes from our investment managers, which are based on proprietary valuation models of independent pricing services. These models generally use inputs such as observable market data, quoted market prices for similar instruments or historical pricing trends of securities relative to our peers. To validate the fair value determinations provided by our investment managers, we review the pricing movement in the context of overall market trends and trading information from our investment managers. In addition, we assess the inputs and methods used in determining the fair value in order to determine the classification of securities in the fair value hierarchy. We had no Level 3 securities either as of December 31, 2023 or 2022. There were no transfers within the hierarchies during the years ended December 31, 2023 or 2022. The following tables set forth our financial instruments measured at fair value on a recurring basis by level within the fair value hierarchy at December 31, 2023 and 2022: December 31, 2023 Fair Value Amortized Gross Gross Fair Assets (in thousands) Cash and cash equivalents: Cash Level 1 $ 50,003 $ — $ — $ 50,003 Money market funds Level 1 47,357 — — 47,357 Commercial paper Level 2 300,256 — ( 165 ) 300,091 Total cash and cash equivalents 397,616 — ( 165 ) 397,451 Investments: U.S. Treasury securities Level 1 481,704 422 ( 44 ) 482,082 Commercial paper Level 2 102,435 7 ( 35 ) 102,407 Corporate debt Level 2 133,523 168 ( 42 ) 133,649 Asset backed securities Level 2 23,963 18 — 23,981 U.S. government agency securities Level 2 103,484 — ( 152 ) 103,332 Total investments 845,109 615 ( 273 ) 845,451 Total assets measured at fair value $ 1,242,725 $ 615 $ ( 438 ) $ 1,242,902 December 31, 2022 Fair Value Amortized Gross Gross Fair Assets (in thousands) Cash and cash equivalents: Cash Level 1 $ 56,198 $ — $ — $ 56,198 Money market funds Level 1 680,934 — — 680,934 Commercial paper Level 2 92,581 — ( 34 ) 92,547 U.S. government agency securities Level 2 4,978 — — 4,978 Total cash and cash equivalents 834,691 — ( 34 ) 834,657 Investments: U.S. Treasury securities Level 1 37,651 — ( 70 ) 37,581 Commercial paper Level 2 28,161 — ( 17 ) 28,144 Corporate debt Level 2 25,402 — ( 131 ) 25,271 Asset backed securities Level 2 6,954 20 — 6,974 U.S. government agency securities Level 2 25,427 19 ( 148 ) 25,298 Total investments 123,595 39 ( 366 ) 123,268 Total assets measured at fair value $ 958,286 $ 39 $ ( 400 ) $ 957,925 The following table presents the contractual maturities of our investments as of December 31, 2023 (in thousands): December 31, 2023 Fair Value Due in less than one year $ 682,776 Due in one to five years 162,675 Total $ 845,451

Commercial Manufacturing and Su

Commercial Manufacturing and Supply Agreement	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commercial Manufacturing and Supply Agreement	4. Commercial Manufacturing and Supply Agreement On October 13, 2023, Vaxcyte GmbH, a Swiss limited liability company and wholly owned subsidiary of ours, entered into a pre-commercial services and commercial manufacturing supply agreement with Lonza (the “Commercial Manufacturing and Supply Agreement”). Pursuant to the Commercial Manufacturing and Supply Agreement, Lonza will (i) construct and build out a dedicated suite (the “Suite”) at Lonza’s facilities in Visp, Switzerland to manufacture certain key components (including drug substance) for our proprietary PCV franchise and any other products or intermediates Vaxcyte GmbH may choose (collectively, the “Products”) and (ii) maintain and operate the Suite (utilizing Lonza’s employees) to manufacture the Products as a service provided to Vaxcyte GmbH, including conducting related quality control and quality assurance operations. Lonza will be a preferred, non-exclusive, supplier of the Products to Vaxcyte GmbH, and Vaxcyte GmbH retains the right to procure the Products from one or more alternate and/or backup manufacturers of the Products (including at our own facilities). Under the Commercial Manufacturing and Supply Agreement, prior to completion of construction and certification of the Suite for commercial operation, Vaxcyte GmbH will contribute to the capital expenditure costs to construct the Suite (and will own certain equipment in the Suite to be purchased or otherwise acquired by Vaxcyte GmbH), and will pay Lonza a fixed-rate monthly service fee for Lonza’s pre-commercial services prior to commencement of commercial operations (which monthly service fee amount is subject to increases in subsequent years). Following commencement of commercial operations of the Suite to manufacture the Products, Vaxcyte GmbH will pay Lonza (i) Suite fees based on allocations of certain of Lonza’s costs to maintain the facility in which the Suite is located and to provide shared services to Vaxcyte GmbH and Lonza’s other customers in such facility, (ii) service fees based upon Lonza’s actual full-time equivalent employee (“FTE”) costs to operate the Suite to manufacture the Products, and (iii) certain other pass-through costs, including for raw materials. In addition, Vaxcyte GmbH may be obligated to pay or reimburse Lonza for certain other fees and expenses under the Commercial Manufacturing and Supply Agreement. Lonza will be eligible for certain financial bonuses, and subject to certain financial penalties, as incentives for the timely completion of certain scale-up activities, receipt of certain regulatory approvals for the Suite and manufacture of the Products in accordance with Vaxcyte GmbH’s commercial requirements. Unless earlier terminated, the Commercial Manufacturing and Supply Agreement will remain in effect until December 31, 2038 , subject to automatic renewal for up to three additional renewal periods of five years each, unless Vaxcyte GmbH elects not to renew (with 24 months advanced notice to Lonza). Vaxcyte GmbH is permitted to terminate the Commercial Manufacturing and Supply Agreement for convenience or for Lonza’s uncured material breach, in each case subject to certain notice obligations. Lonza is permitted to terminate the Commercial Manufacturing and Supply Agreement in the event that Vaxcyte GmbH commits certain specified material breaches, including uncured failure to pay material, undisputed amounts of money due to Lonza, subject to certain notice obligations. Either party may terminate the Commercial Manufacturing and Supply Agreement in certain circumstances in the event of the other party’s bankruptcy. In the event that Vaxcyte GmbH terminates the agreement for convenience, or Lonza terminates the agreement in the event that Vaxcyte GmbH commits certain specified material breaches, then certain termination consequences may be triggered, including that (i) Vaxcyte GmbH would forfeit any outstanding entitlement to credit from Lonza of the Repurposing Fee (as defined below), and (ii) Vaxcyte GmbH would be obligated to pay Lonza a termination penalty equal to the greater of (a) CHF 70,000,000 , or (b) a prespecified number of months’ FTE fees for the actual FTEs assigned to Vaxcyte GmbH as of the date of termination. Within 30 days of the Effective Date, Vaxcyte GmbH paid Lonza a repurposing fee (the “Repurposing Fee”) of CHF 27,000,000 that will be credited back to Vaxcyte GmbH over a 10-year period starting upon commencement of commercial production. In the event of a termination under certain circumstances, Lonza shall be obligated to provide certain wind-down and transition services to Vaxcyte GmbH for up to 12 and 24 months, respectively. Construction and buildout has commenced on the Suite and, as of December 31, 2023, we have incurred (i) $ 51.8 million of capital expenditures related to the facility buildout and equipment which is Vaxcyte owned and which have been recorded as manufacturing facility and equipment construction-in-progress under Property and equipment, net on our consolidated balance sheets (see Note 5 “Balance Sheet Details”) and (ii) $ 34.7 million of facility buildout expenditures that are owned and controlled by Lonza, which have been accounted for as prepaid lease payments within Other assets on our consolidated balance sheets, captioned as manufacturing facility construction buildout, and will be recorded as a right-of-use asset under ASC 842 lease accounting when the buildout of the Suite is complete and manufacturing activities commence, at which point we will control the Lonza owned Suite and pre-existing equipment (see Note 5 “Balance Sheet Details”). Included in the Lonza owned capital expenditures are pre-commercial services fees of CHF 3 million and the Repurposing Fee of CHF 27 million, which is intended to cover Lonza’s expenses in making the Suite available to lease to other Lonza customers in the event of early termination by us.

Balance Sheet Details

Balance Sheet Details	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Details	5. Balance Sheet Details Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets as of December 31, 2023 and 2022 consisted of the following: December 31, December 31, 2023 2022 (in thousands) Prepaid expenses $ 6,159 $ 5,312 Purchased equipment deposits 3,856 — Interest receivable 3,598 2,848 Grant receivable 9 1,029 Other current assets 2,105 1,990 Total $ 15,727 $ 11,179 Property and Equipment, Net Property and equipment, net as of December 31, 2023 and 2022 consisted of the following: December 31, 2023 2022 (in thousands) Furniture and equipment $ 1,608 $ 1,608 Computers and computer software 771 416 Lab equipment 25,110 13,100 Leasehold improvements 1,460 1,353 Manufacturing equipment and auxiliary 8,134 — Manufacturing facility and equipment construction-in-progress (1) 51,815 — Total property and equipment 88,898 16,477 Less: accumulated depreciation and amortization ( 9,272 ) ( 6,117 ) Property and equipment, net $ 79,626 $ 10,360 ____________ (1) See Note 4, “ Commercial Manufacturing and Supply Agreement, ” for further details. Depreciation and amortization expense for the years ended December 31, 2023, 2022 and 2021 was $ 3.2 million, $ 2.6 million and $ 1.8 million, respectively. Other Assets Other assets as of December 31, 2023 and 2022 consisted of the following: December 31, December 31, 2023 2022 (in thousands) Manufacturing facility construction buildout (1) $ 34,688 $ — Long-term prepaid assets 2,768 4,361 Other long-term assets 106 194 Total $ 37,562 $ 4,555 _____________ (1) See Note 4, “ Commercial Manufacturing and Supply Agreement, ” for further details. Accrued Expenses Accrued expenses as of December 31, 2023 and 2022 consisted of the following: December 31, 2023 2022 (2) (in thousands) Clinical studies $ 2,156 $ 1,518 Other research and development 30,759 7,446 Acquired manufacturing rights (1) 25,000 5,000 Other accrued expenses 1,900 1,411 Total $ 59,815 $ 15,375 ______________ (1) See Note 7, “ Commitments and Contingencies, Sutro Option Agreement, ” for further details. (2) The breakout and categorizations of the 2022 total accrued expenses have been updated to conform to the 2023 presentation.

Leases

Leases	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Leases	6. Leases Operating Lease Obligations In October 2023, we entered into the Commercial Manufacturing and Supply Agreement. We have concluded that this agreement contains an embedded lease and will be accounted for in accordance with Accounting Standards Codification (“ASC”) 842 Leases upon the commencement date. As of December 31, 2023, the lease had not commenced and, as such, no lease liability or ROU asset was recorded on the consolidated balance sheets and no operating lease expense was recorded on the consolidated statements of operations. See Note 4, “Commercial Manufacturing and Supply Agreement,” for further details. In September 2023, we entered into an assignment and assumption of lease agreement (the “Assignment Agreement”) for a new operating lease in the same building as our current corporate headquarters (the “Assumed Lease Premises”). The assumed lease has an original contractual term of 10 years, expiring on November 30, 2031 , unless earlier terminated. Pursuant to the Assignment Agreement, the base rent was abated for three full calendar months following the October 1, 2023 effective date of the Assignment Agreement. Thereafter, we are obligated to pay an aggregate of approximately $ 1.9 million in rent payments for the remaining nine months of the first year, with a 3 % rent adjustment (not inclusive of rent abatement) every year thereafter. Upon commencement of the lease in October 2023, we recorded a ROU asset and lease liability of $ 16.7 million and $ 16.8 million, respectively. In January 2021, we entered into a lease agreement for our current corporate headquarters facility located in San Carlos, California and a license agreement for temporary lab and office space in Palo Alto, California. The lease term for our current corporate headquarters facility began on December 3, 2021 and expires on December 31, 2025 . We have two 60 -month renewal options. We extended the license agreement for our temporary headquarters in the Palo Alto office by 60 days to March 3, 2022 to accommodate our relocation plan. The original term of the license agreement for the temporary space in Palo Alto terminated when the San Carlos office leasehold improvements were completed and we moved into our current corporate headquarters. These two agreements are accounted for as a combined lease because the contracts were negotiated as a package with the same commercial objective. Upon commencement of the San Carlos lease in December 2021, we recorded a ROU asset and lease liability of $ 28.4 million and $ 12.9 million, respectively. In July 2016, we entered into a five-year lease agreement for our previous headquarters facility located in Foster City, California. The original term of the lease was from September 1, 2016 to August 31, 2021 , with two 30 -month renewal options . In July 2019, we leased another facility in Foster City, California. The original term of this lease was from July 1, 2019 to October 31, 2021 , with no renewal options . In November 2020, we extended the terms of these leases for six months to March 1, 2022 and April 30, 2022 , respectively. In February 2022, we entered into an early termination agreement for one of the facilities in Foster City and terminated our lease on February 12, 2022 instead of April 30, 2022. Information related to our ROU assets and related lease liabilities was as follows (dollar amounts in thousands): December 31, December 31, 2023 2022 Cash paid for operating lease liabilities $ 7,390 $ 5,374 Operating lease right-of-use assets $ 30,997 $ 21,288 Operating lease liabilities - current $ 7,113 $ 5,910 Operating lease liabilities - long-term 22,111 12,031 Total lease liabilities $ 29,224 $ 17,941 Weighted-average remaining lease term (in years) 5.71 2.78 Weighted-average discount rate 8.4 % 7.6 % Maturities of lease liabilities as of December 31, 2023 were as follows: Years ending December 31, (in thousands) 2024 $ 8,817 2025 9,836 2026 2,899 2027 2,986 2028 3,075 Thereafter 9,503 Total future undiscounted lease payments 37,115 Less: Imputed interest ( 7,891 ) Total lease liabilities $ 29,224 Rent expense recognized under the leases was $ 8.5 million, $ 7.9 million and $ 3.2 million for the years ended December 31, 2023 , 2022 and 2021, respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Legal Contingencies From time to time, we may become involved in legal proceedings arising from the ordinary course of business. We record a liability for such matters when it is probable that future losses will be incurred and that such losses can be reasonably estimated. Significant judgment by us is required to determine both probability and the estimated amount. We do not believe that there is any litigation or asserted or unasserted claim pending that could, individually or in the aggregate, have a material adverse effect on our results of operations or financial condition. Guarantees and Indemnifications In the normal course of business, we enter into agreements that contain a variety of representations and provide for general indemnification. Our exposure under these agreements is unknown because it involves claims that may be made against us in the future. To date, we have not paid any claims or been required to defend any action related to our indemnification obligations. As of December 31, 2023 and 2022, we did not have any material indemnification claims that were probable or reasonably possible and consequently have not recorded related liabilities. Indemnification To the extent permitted under Delaware law, we have agreed to indemnify our directors and officers for certain events or occurrences while the director or officer is, or was, serving at our request in such capacity. The indemnification period covers all pertinent events and occurrences during the director’s or officer’s service. The maximum potential amount of future payments we could be required to make under these indemnification agreements is not specified in the agreements; however, we have directors and officers insurance coverage that reduces our exposure and enables us to recover a portion of any future amounts paid. We have not incurred any material costs as a result of such indemnification and are not currently aware of any indemnification claims. Development and Manufacturing Services Agreements with Lonza In April 2022, we entered into a non-exclusive development and manufacturing services agreement with Lonza effective as of March 22, 2022, which was subsequently amended on May 12, 2022, November 21, 2022 and October 31, 2023 (as amended, the “2022 Lonza DMSA”). Pursuant to the 2022 Lonza DMSA, Lonza is obligated to perform services including manufacturing process development and clinical manufacture and supply of our proprietary PCV candidates. Subject to the terms and conditions set forth in the 2022 Lonza DMSA, Lonza has granted to us a non-exclusive, worldwide, fully paid-up, irrevocable, transferable license, including the right to grant sublicenses, under the New General Application Intellectual Property, to research, develop, make, have made, use, sell and import the Product. Unless earlier terminated, the 2022 Lonza DMSA shall remain in place for a period of five years. Either party may terminate the 2022 Lonza DMSA for any reason on prior written notice to the other party, provided that Lonza may not exercise such right until a specified future date. In addition, either party may terminate the 2022 Lonza DMSA (i) within a given time period upon any material breach that is left uncured by the other party, or (ii) immediately if the other party becomes insolvent. We may also terminate the 2022 Lonza DMSA upon an extended force majeure event. Upon expiration and/or termination of the 2022 Lonza DMSA and/or any purchase order, we will pay Lonza for all service rendered, all costs incurred, all unreimbursed capital equipment and any cancellation fees (each term as defined in the 2022 Lonza DMSA). In February 2023, we entered into another non-exclusive development and manufacturing services agreement with Lonza effective as of March 1, 2023 (the “2023 Lonza DMSA”). Pursuant to the 2023 Lonza DMSA, Lonza will perform manufacturing process development and the manufacture of components for VAX-24 and VAX-31, including the polysaccharide antigens, our proprietary eCRM protein carrier and conjugated drug substances. Subject to the terms and conditions set forth in the 2023 Lonza DMSA, Lonza has granted to us a non-exclusive, worldwide, fully paid-up, transferable license, including the right to grant sublicenses (subject to the prior written consent of Lonza), under the New General Application Intellectual Property, to use, sell and import the Product manufactured under the 2023 Lonza DMSA (but no other products). Unless earlier terminated, the 2023 Lonza DMSA shall remain in place for a period of five years and shall automatically renew for one additional two-year period unless either party provides written notice of non-renewal at least two years prior to the fifth anniversary of the effective date. We may terminate the 2023 Lonza DMSA for any reason on prior written notice to the other party on a Project Plan-by-Project Plan basis. Either party may terminate the 2023 Lonza DMSA (i) within a given time period upon any material breach that is left uncured by the other party, (ii) immediately if the other party becomes insolvent, is dissolved or liquidated, makes a general assignment for the benefit of its creditors, or files or has filed against it, a petition in bankruptcy or has a receiver appointed for a substantial part of its assets, (iii) upon an extended force majeure event, or (iv) if it becomes apparent to either party at any stage in the provision of the Services that it will be impossible to complete the Services for scientific or technical reasons despite exercise of best commercial efforts by both parties. Pursuant to the reason for termination and the party initiating the termination, we will pay Lonza for some combination of services rendered, costs incurred, unreimbursed capital equipment and/or any cancellation fees. Upon an extended force majeure event, neither party shall have any further liability to the other party (each term as defined in the 2023 Lonza DMSA). Under each of the 2022 Lonza DMSA and 2023 Lonza DMSA (collectively, the “Lonza Agreements”) we pay Lonza agreed-upon fees for their performance of development and manufacturing services and pass through expenses incurred by Lonza for raw materials, as well as customary procurement and handling fees. Under each Lonza Agreement, we own all rights, title and interest in and to any and all New Customer Intellectual Property (as defined in each Lonza Agreement), and Lonza owns all right, title and interest in New General Application Intellectual Property (as defined in each Lonza Agreement). Commercial Manufacturing and Supply Agreement with Lonza For details of the Commercial Manufacturing and Supply Agreement with Lonza, see Note 4. Sutro Option Agreement In December 2022, we entered into Option Agreement with Sutro Biopharma. Pursuant to the Option Agreement, we acquired from Sutro Biopharma (i) authorization to enter into an agreement with an independent alternate CMO to directly source Sutro Biopharma’s cell-free extract, allowing us to have direct oversight over financial and operational aspects of the relationship with the CMO; and (ii) the “Option. We and Sutro Biopharma agreed to negotiate the terms and conditions of a form definitive agreement to be entered into in the event we exercise the Option, which would include the terms and conditions set forth in an executed term sheet between us (the “Term Sheet”) and such terms that were necessary to give effect to each of the terms and conditions set forth in the Term Sheet (the “Form Definitive Agreement”). The Option period was five years from the date of the Option Agreement, subject to potential acceleration in the event we undergo a change of control. As consideration for the Option and other rights and authorizations granted to us under the Option Agreement, we paid Sutro Biopharma upfront consideration of $ 22.5 million, consisting of (i) $ 10.0 million in cash and $ 7.5 million worth of shares of our common stock (the number of shares to be calculated based on the arithmetic average of the daily volume weighted average price of our common stock as traded on Nasdaq in the three consecutive trading days immediately prior to the issuance thereof), and (ii) $ 5.0 million payable within five business days after we and Sutro Biopharma mutually agree in writing upon the Form Definitive Agreement. The 167,780 shares of common stock issued was recorded at fair value of $ 8.0 million on the date of settlement, December 22, 2022. In the event that we elected to exercise the Option, we agreed to pay Sutro Biopharma an aggregate Option exercise price of $ 75.0 million in cash in two installments and, upon the occurrence of certain regulatory milestones, certain additional milestone payments totaling up to $ 60.0 million in cash. On September 28, 2023, we and Sutro Biopharma mutually agreed in writing upon the Form Definitive Agreement to become effective in the event that we exercise the Option and, on October 2, 2023, we paid the $ 5.0 million accrued commitment. On November 21, 2023 (the “Option Exercise Date”), we exercised the Option by submitting written notice thereof to Sutro Biopharma and concurrently paid Sutro Biopharma $ 50.0 million in cash as the first of two installment payments for the Option exercise price. Under the Option Agreement, we are obligated to pay Sutro an additional $ 25.0 million in cash within six months of the Option Exercise Date as the second of two installment payments for the Option exercise. This has been accrued on our consolidated balance sheets as of December 31, 2023. Upon the occurrence of certain regulatory milestones, we would be obligated to pay Sutro Biopharma certain additional milestone payments totaling up to $ 60.0 million in cash. In the event that we undergo a change of control, certain rights and payments may be accelerated. As of December 31, 2023, we have paid $ 50 million, the remaining $ 25 million is accrued as of December 31, 2023. We determined there is no current alternative future use of the acquired manufacturing rights from the Option Agreement. As a result, the amounts paid and accrued for were expensed as incurred. Manufacturing Rights Agreement with Sutro Biopharma Concurrent with the payment of the first installment of the Option exercise price pursuant to the Option Agreement, on November 21, 2023, the manufacturing rights agreement (in the form of the Form Definitive Agreement) between us and Sutro Biopharma (the “Manufacturing Rights Agreement”) became effective. Under the Manufacturing Rights Agreement, we received an exclusive (except as to Sutro Biopharma), perpetual (subject to termination), worldwide license, for no additional royalty (i.e., royalty-free, other than any royalties due under the Sutro Biopharma License Agreement), under Sutro Biopharma’s relevant patents and know-how, to manufacture or have manufactured extract and improvements to extract (in any form) solely for use in the research, development, use, production, sale, offering for sale, export, import, commercialization or other exploitation of Vaccine Compositions (as defined in the Sutro Biopharma License Agreement) (as well as certain rights with respect to certain regulatory matters related to extract and its use in connection with such Vaccine Compositions). We have the right to extend our rights and obligations under the Manufacturing Rights Agreement to our affiliates and to sublicense our rights to manufacture extract and improvements to extract to certain third-party CMOs and other contractors (for our benefit and not for such third party’s independent commercial use). For clarity, we are not permitted to manufacture extract for sale to third parties for the independent use of such third parties. Under the Manufacturing Rights Agreement, we have the obligation to protect the confidentiality of the extract manufacturing technology, and Sutro Biopharma has certain audit rights in connection therewith. Under the Manufacturing Rights Agreement, upon our request and at our cost, Sutro Biopharma will support up to two technology transfers to us (or to an affiliate of ours or certain third-party CMOs designated by us) of certain Sutro Biopharma know-how, materials and information to enable us to manufacture or have manufactured extract. Under certain circumstances, Sutro Biopharma may source extract from us or certain third-party CMOs, subject to reimbursement for technology transfer costs. The Manufacturing Rights Agreements contains certain terms with respect to the ownership, prosecution, maintenance and enforcement of certain intellectual property rights licensed or arising under the Manufacturing Rights Agreement, which are generally consistent with the Sutro Biopharma License Agreement. Unless earlier terminated, the Manufacturing Rights Agreement will remain in effect in perpetuity. Sutro Biopharma may only terminate the Manufacturing Rights Agreement in the event of our (i) uncured, intentional, material breach of certain confidentiality provisions resulting in actual, material harm to Sutro Biopharma’s business, (ii) uncured, intentional material breach of certain provisions relating to the use of certain of Sutro Biopharma’s know-how outside of the Vaccine Field, (iii) unintentional, material breach of certain provisions relating to the use of certain of Sutro Biopharma’s know-how outside of the Vaccine Field that we do not use reasonable best efforts to cease and (to the extent reasonably curable) cure in a timely fashion, or (iv) uncured failure to pay the Option exercise price or any undisputed milestone payment under the Option Agreement when due. We may terminate the Manufacturing Rights Agreement at our discretion upon 60 days’ written notice, and both parties may terminate the Manufacturing Rights Agreement upon mutual written consent. Purchase Commitments We enter into agreements in the normal course of business with CMOs and other vendors for manufacturing services and raw materials purchases. We rely on several third-party manufacturers for our manufacturing requirements. As of December 31, 2023, we had the following amounts of non-cancelable purchase commitments related to manufacturing services and raw materials purchased due to our key manufacturing partners. These amounts represent our minimum contractual obligations, including termination fees. If we terminate certain firm orders with key manufacturing partners, we will be required to pay for the manufacturing services scheduled or raw materials purchased under our arrangements. The actual amounts we pay in the future to our vendors under such agreements may differ from the purchase order amounts. Years ending December 31, (in thousands) 2024 $ 181,812 2025 41,840 2026 1,296 2027 414 Total non-cancelable purchase commitments due to key manufacturing partners $ 225,362

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Stockholders' Equity	8. Stockholders' Equity Preferred Stock Our certificate of incorporation authorizes us to issue up to 10,000,000 shares of preferred stock with $ 0.001 par value per share. There were no shares preferred stock issued or outstanding as of December 31, 2023 and 2022. Our board of directors (“Board”) are authorized to provide for the issue of all or any of the shares of preferred stock in one or more series, and to fix, determine or alter the voting powers, designation, preferences and rights of the preferred shares, and the qualifications, limitations or restrictions of any wholly unissued shares, to establish from time to time the number of shares constituting any such series, and to increase or decrease the number of shares, if any. Holders of outstanding shares of preferred stock shall be entitled to receive dividends, when, and as declared by the Board in preference and priority to any declaration or payment of any distribution on common stock. The right to receive dividends on preferred shares of preferred stock shall not be cumulative and no right to dividends shall accrue to holders of preferred stock. No dividends have been paid or declared as of December 31, 2023 and 2022. Common Stock Our certificate of incorporation authorizes us to issue up to 500,000,000 shares of common stock with $ 0.001 par value per share, of which 95,364,831 and 79,470,670 shares were issued and outstanding as of December 31, 2023 and 2022, respectively. The holders of our common stock are also entitled to receive dividends whenever funds are legally available, when and if declared by our Board. As of December 31, 2023 and 2022, no dividends have been declared. Each share of common stock is entitled to one vote . In July 2021, we entered into an Open Market Sales Agreement SM (the “Original ATM Sales Agreement”) with Jefferies LLC (“Jefferies”) which provided that, upon the terms and subject to the conditions and limitations set forth in the Original ATM Sales Agreement, we may elect to issue and sell, from time to time, shares of our common stock having an aggregate offering price of up to $ 150.0 million through Jefferies acting as our sales agent or principal. As of February 27, 2023, we had sold 4,995,709 shares of our common stock under the Original ATM Sales Agreement at an average price of $ 27.57 per share for aggregate gross proceeds of $ 137.8 million. On February 27, 2023, we and Jefferies entered into an amendment to the Original ATM Sales Agreement (as amended, the “Amended ATM Sales Agreement”) pursuant to which we may offer and sell shares of our common stock having an aggregate offering price of up to $ 400.0 million, which is in addition to the $ 150.0 million aggregate offering price under the Original ATM Sales Agreement. The material terms and conditions of the Original ATM Sales Agreement otherwise remain unchanged. We will pay Jefferies a commission of up to 3.0 % of the gross sales proceeds of any common stock sold through Jefferies under the Amended ATM Sales Agreement; however, we are not obligated to make any sales of common stock. As of December 31, 2023 , we have sold 1,588,807 shares of our common stock under the Amended ATM Sales Agreement at an average price of $ 44.06 per share for aggregate gross proceeds of $ 70.0 million ($ 68.6 million net of commissions and offering expenses). On January 13, 2022, we completed an underwritten public offering in which we issued 2,500,000 shares of our common stock at a price of $ 20.00 per share and pre-funded warrants to purchase 2,500,000 shares of our common stock at a price of $ 19.999 per underlying share. In February 2022, the underwriters exercised their option to purchase an additional 750,000 shares of common stock. In aggregate, we received $ 107.6 million in net proceeds after deducting underwriting discounts and commissions and other offering expenses payable by us, and excluding the exercise of any pre-funded warrants. On October 28, 2022, we completed an underwritten public offering of 17,812,500 shares of our common stock, which included the full exercise of the underwriters’ option to purchase an additional 2,812,500 shares, at a price of $ 32.00 per share and pre-funded warrants to purchase 3,750,000 shares of our common stock at a price of $ 31.999 per underlying share. In aggregate, we received $ 651.6 million in net proceeds after deducting underwriting discounts and commissions and other offering expenses payable by us, and excluding the exercise of any pre-funded warrants. On April 21, 2023, we completed an underwritten public offering of 13,030,000 shares of our common stock, which included the full exercise of the underwriters’ option to purchase an additional 1,830,000 shares, at a price of $ 41.00 per share and pre-funded warrants to purchase 1,000,000 shares of our common stock at a price of $ 40.999 per underlying share. In aggregate, we received $ 545.3 million in net proceeds after deducting underwriting discounts and commissions and other offering expenses payable by us, and excluding the exercise of any pre-funded warrants. Common stock reserved for future issuances under the 2020 Equity Incentive Plan (the “2020 Plan”) and the 2014 Equity Incentive Plan (the “2014 Plan”) was as follows, and excludes 36,710 shares issued outside of the 2014 Plan and 2020 Plan: December 31, December 31, 2023 2022 Options issued and outstanding 9,314,836 7,715,494 Restricted stock units issued and outstanding 753,462 456,766 Shares available for future stock option grants 6,065,150 4,679,598 Total 16,133,448 12,851,858

Pre-Funded Warrants

Pre-Funded Warrants	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Pre-Funded Warrants	9. P re-Funded Warrants In connection with our underwritten public offering in January 2022, we issued pre-funded warrants to purchase 2,500,000 shares of our common stock at a price of $ 19.999 per underlying share. Each pre-funded warrant has an exercise price of $ 0.001 per share. In connection with our underwritten public offering in October 2022, we issued pre-funded warrants to purchase 3,750,000 shares of our common stock at a price of $ 31.999 per underlying share. Each pre-funded warrant has an exercise price of $ 0.001 per share. In connection with our underwritten public offering in April 2023, we issued pre-funded warrants to purchase 1,000,000 shares of our common stock at a price of $ 40.999 per underlying share. Each pre-funded warrant has an exercise price of $ 0.001 per share. The public offering prices for the pre-funded warrants were equal to the public offering prices of our common stock, less the $ 0.001 exercise price of each pre-funded warrant and were recorded as a component of stockholders' equity within additional paid-in-capital. The pre-funded warrants are exercisable, at the option of each holder, in whole or in part by delivering to us a duly executed exercise notice and payment of the exercise price. No fractional shares of common stock will be issued in connection with the exercise of a pre-funded warrant. The holders of the pre-funded warrants may also satisfy their obligation to pay the exercise price through a “cashless exercise,” in which the holder receives the net value of the pre-funded warrant in shares of common stock determined according to the formula set forth in the pre-funded warrant. The pre-funded warrants will not expire until they are fully exercised. However, we may not effect the exercise of any pre-funded warrants, and a holder will not be entitled to exercise any portion of any pre-funded warrants that, upon giving effect to such exercise, would cause: (i) the aggregate number of shares of our common stock beneficially owned by such holder (together with affiliates) to exceed 4.99 % or 9.99 % of the number of shares of our common stock outstanding immediately after giving effect to the exercise, as applicable; or (ii) the combined voting power of our securities beneficially owned by such holder (together with its affiliates) to exceed 4.99 % or 9.99 % of the combined voting power of all of our securities outstanding immediately after giving effect to the exercise, as applicable, as such percentage ownership is determined in accordance with the terms of the pre-funded warrants. However, any holder of a pre-funded warrant may increase or decrease such percentage to any other percentage not in excess of 19.99 % upon at least 61 days' prior notice for the holder to us. As of December 31, 2023 , no shares underlying the pre-funded warrants had been exercised.

Equity Incentive Plans

Equity Incentive Plans	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Equity Incentive Plans	10. Equity Incentive Plans 2020 and 2014 Equity Incentive Plans In June 2020, our Board adopted, and our stockholders approved, the 2020 Plan, which became effective on June 11, 2020. Under the 2020 Plan, we may grant stock options, appreciation rights, restricted stock and restricted stock units (RSUs) to employees, consultants and directors. Stock options granted under the 2020 Plan may be either incentive stock options or nonqualified stock options. Incentive stock options may be granted only to our employees, including officers and directors who are also employees. Nonqualified stock options may be granted to our employees, officers, directors, consultants and advisors. The exercise price of stock options granted under the 2020 Plan must be at least equal to the fair market value of the common stock on the date of grant, except that an incentive stock option granted to an employee who owns more than 10 % of the shares of our common stock shall have an exercise price of no less than 110 % of the fair value per share on the grant date and expire five years from the date of grant. The maximum term of stock options granted under the 2020 Plan is 10 years, unless subject to the provisions regarding 10 % stockholders. Our stock options granted to new employees generally vest over four years at a rate of 25 % upon the first anniversary of the vesting commencement date and monthly thereafter. Our other stock options granted to employees generally vest on terms consistent with stock options granted to new employees or monthly over four years from the vesting commencement date. Our RSUs granted to new employees generally vest over four years at a rate of 25 % upon one year from the grant date, then 12.5 % every six months thereafter. Our other RSUs granted to employees generally vest over three and a half years at a rate of 25 % upon six months from the grant date, then 12.5 % every six months thereafter. A total of 10,150,000 shares of common stock were approved to be initially reserved for issuance under the 2020 Plan. The number of shares that remained available for issuance under the 2014 Plan as of the effective date of the 2020 Plan, and shares subject to outstanding awards under the 2014 Plan as of the effective date of the 2020 Plan that are subsequently canceled, forfeited or repurchased by us, will be added to the shares reserved under the 2020 Plan. In addition, the number of shares of common stock available for issuance under the 2020 Plan is automatically increased on the first day of each calendar year during the 10-year term of the 2020 Plan, beginning with January 1, 2021 and ending with January 1, 2030, by an amount equal to 5 % of the outstanding number of shares of our common stock on December 31 of the preceding calendar year or such lesser amount as determ ined by our Board. As of December 31, 2023, an aggregate of 6,065,150 shares of common stock were available for issuance under the 2020 Plan. Effective January 1, 2024, the number of shares of common stock available under the 2020 Plan increased by 4,768,241 shares pursuant to the evergreen provision of the 2020 Plan. Our 2014 Plan permitted the granting of incentive stock options, non-statutory stock options, restricted stock and other stock-based awards. Subsequent to the adoption of the 2020 Plan, no additional equity awards can be made under the 2014 Plan. Shares reserved and remaining available for issuance under the 2014 Plan were added to the 2020 Plan reserve upon its effectiveness. The terms of the 2014 Plan permit the exercise of options granted prior to vesting, subject to required approvals. The unvested shares are subject to our lapsing repurchase right upon termination of employment at the original purchase price. Shares purchased by employees pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be issued until those shares vest according to their respective vesting schedules. Cash received for early exercised stock options is recorded as other liabilities on the consolidated balance sheets and is reclassified to common stock and additional paid-in capital as such shares vest. As of December 31, 2023, 2,227,963 shares and 7,840,335 shares of common stock were subject to outstanding options and RSUs under the 2014 Plan and 2020 Plan, respectively. At December 31, 2023 and 2022, 0 and 3,705 shares, respectively, remained subject to our right of repurchase as a result of the early exercised stock options. The remaining liabilities related to early exercised shares as of December 31, 2023 and 2022 were both less than $ 0.1 million and were recorded in other liabilities. Stock Option Activity Stock option activity under our 2020 Plan and 2014 Plan, which excludes options to purchase 36,710 shares granted outside of the 2020 Plan and 2014 Plan, was as follows: Options Outstanding Stock Option and Restricted Stock Units Activity Options Number Weighted- Weighted- Aggregate Balances — December 31, 2021 6,104,756 5,295,007 $ 9.30 Additional shares authorized 2,651,598 — Options granted ( 3,850,981 ) 3,850,981 $ 27.67 Options exercised 385 (1) ( 1,153,285 ) $ 4.25 Options forfeited 277,209 ( 277,209 ) $ 23.54 Restricted Stock Units granted ( 581,047 ) Restricted Stock Units withheld 32,626 Restricted Stock Units forfeited 45,052 Balances — December 31, 2022 4,679,598 7,715,494 $ 18.70 8.20 $ 225,667 Additional shares authorized 3,973,533 Options granted ( 2,343,037 ) 2,343,037 $ 44.44 Options exercised 1,080 (1) ( 538,888 ) $ 10.50 Options forfeited 204,807 ( 204,807 ) $ 32.58 Restricted Stock Units granted ( 574,123 ) Restricted Stock Units withheld 78,755 Restricted Stock Units forfeited 44,537 Balances — December 31, 2023 6,065,150 9,314,836 $ 25.35 7.75 $ 348,868 Vested and expected to vest — December 31, 2023 9,314,836 $ 25.35 7.75 $ 348,868 Exercisable at December 31, 2023 4,646,989 $ 16.40 6.80 $ 215,608 ______________________________________ (1) Shares returned due to net exercises . During the years ended December 31, 2023, 2022 and 2021, options to purchase 538,888 , 1,153,285 and 926,514 shares of common stock, respectively, were exercised for cash at a weighted-average price per share of $ 10.50 , $ 4.25 and $ 3.25 , respectively. The weighted-average grant date fair value of options granted for the years ended December 31, 2023, 2022 and 2021 was $ 28.74 , $ 18.88 and $ 14.65 , respectively. The intrinsic value of the stock options exercised was $ 21.2 million, $ 34.0 million and $ 18.9 million for the years ended December 31, 2023, 2022 and 2021, respectively. Restricted Stock Units Activity In March 2022, our Board authorized the issuance of RSUs under our 2020 Plan and adopted a form of Restricted Stock Unit Grant Notice and Restricted Stock Unit Award Agreement (the "RSU Agreement"), which is intended to serve as a standard form agreement for RSU grants issued to employees. RSU activity for the years ended December 31, 2023 and 2022 was as follows: Shares Weighted- Unvested at December 31, 2021 — $ — Granted 581,047 26.25 Vested and released ( 79,229 ) 24.79 Cancelled ( 45,052 ) 24.32 Unvested at December 31, 2022 456,766 $ 26.70 Granted 574,123 45.57 Vested and released ( 232,890 ) 30.97 Cancelled ( 44,537 ) 40.78 Unvested at December 31, 2023 753,462 $ 38.93 The weighted-average grant date fair value of RSUs granted during the year ended December 31, 2023 and December 31, 2022 was $ 45.57 and $ 26.25 , respectively. The aggregate fair value of unvested RSUs is calculated using the closing price of our common stock on the grant date. As of December 31, 2023 and December 31, 2022, the unrecognized stock-based compensation cost of unvested RSUs was $ 25.9 million and $ 10.8 million, respectively, which is expected to be recognized over a weighted-average period of 2.7 years and 3.0 years, respectively. 2020 Employee Stock Purchase Plan In June 2020, our Board adopted, and our stockholders approved, the 2020 Employee Stock Purchase Plan (the “2020 ESPP”), which became effective on June 11, 2020. The 2020 ESPP permits participants to purchase common stock through payroll deductions of up to 15 % of their eligible compensation. Employees enrolled in the 2020 ESPP purchase shares of common stock at a price per share equal to 85 % of the lower of the fair market value at the start or end of the six-month purchase periods within the two-year offering period. A total of 650,000 shares of common stock were approved to be initially reserved for issuance under the 2020 ESPP. In addition, the number of shares of common stock available for issuance under the 2020 ESPP is automatically increased on the first day of each calendar year during the 10-year term of the 2020 Plan, beginning with January 1, 2021 and ending with January 1, 2030, by an amount of 1 % of the outstanding number of shares of our common stock on December 31 of the preceding calendar year or such lesser amount as determined by our Board. Activity under our 2020 ESPP was as follows: Shares Balance - December 31, 2021 1,070,704 Additional shares authorized 530,319 Shares purchased ( 61,709 ) Balance - December 31, 2022 1,539,314 Additional shares authorized 794,706 Shares purchased ( 76,275 ) Balance - December 31, 2023 2,257,745 Effective January 1, 2023, the number of shares of common stock available under the 2020 ESPP increased by 794,706 shares pursuant to the evergreen provision of the 2020 ESPP. There was no increase effective January 1, 2024 as determined by our Board. Stock-based Compensation We estimated the fair value of employee stock options using the Black-Scholes option-pricing model for the years ended December 31, 2023, 2022 and 2021 using the following weighted-average assumptions: Year Ended December 31, 2023 2022 2021 Fair Value Assumptions Expected volatility 71.3 % - 74.0 % 78.1 % - 85.1 % 81.0 % - 84.1 % Expected dividend yield 0 % 0 % 0 % Expected term (in years) 5.3 - 5.4 5.3 - 5.5 5.3 - 5.5 Risk-free interest rate 3.5 % - 4.6 % 1.6 % - 4.4 % 0.5 % - 1.3 % We estimated the fair value of shares under the 2020 ESPP using the Black-Scholes option-pricing model for the years ended December 31, 2023, 2022 and 2021 using the following weighted-average assumptions: Year Ended December 31, 2023 2022 2021 Fair Value Assumptions Expected volatility 38.1 % - 99.7 % 78.8 % - 99.7 % 79.6 % - 126.3 % Expected dividend yield 0 % 0 % 0 % Expected term (in years) 0.5 - 2.0 0.5 - 2.0 0.5 - 2.0 Risk-free interest rate 4.2 % - 5.4 % 0.1 % - 4.7 % 0.0 % - 0.5 % We recorded total stock-based compensation expense for the years ended December 31, 2023, 2022 and 2021 related to the 2014 Plan, the 2020 Plan and the 2020 ESPP in the consolidated statements of operations and allocated the amounts as follows: Year Ended December 31, 2023 2022 2021 (In thousands) Research and development $ 23,275 $ 9,899 $ 3,954 General and administrative 25,485 13,751 6,775 Total $ 48,760 $ 23,650 $ 10,729 As of December 31, 2023, there was $ 127.5 million of unrecognized stock-based compensation expense related to employee and non-employee awards, which is expected to be recognized over a weighted-average period of 2.7 years.

Retirement Plan

Retirement Plan	12 Months Ended
	Dec. 31, 2023
Retirement Benefits [Abstract]
Retirement Plan	11. Retirement Plan We sponsor a qualified 401(k) Plan (the “401(k) Plan”). The 401(k) Plan is a defined contribution plan covering eligible employees. Participants may contribute a portion of their annual compensation limited to a maximum annual amount set by the Internal Revenue Code. The 401(k) Pl an is a safe-harbor plan whereby we make mandatory employer-matching contributions to plan participants’ accounts through payroll. For the years ended December 31, 2023, 2022 and 2021, we contributed $ 1.4 million, $ 0.8 million and $ 0 , res pectively, to the 401(k) Plan.

Funding Arrangement

Funding Arrangement	12 Months Ended
	Dec. 31, 2023
Funding Arrangement [Abstract]
Funding Arrangement	12. Funding Arrangement Our VAX-A1 vaccine development program currently is funded in part by a grant obtained from Combating Antibiotic Resistant Bacteria Biopharmaceutical Accelerator (“CARB-X”), a global non-profit partnership dedicated to accelerating antibacterial innovation to tackle the rising global threat of drug-resistant bacteria. The CARB-X grant provides for total potential funding of up to $ 14.6 million (including $ 11.7 million awarded to date since the grant’s inception in 2019) upon the achievement of VAX-A1 development milestones through June 2024. Our VAX-GI vaccine development program is currently funded in part by two grants obtained from the National Institutes of Health (“NIH”) administered by the University of Maryland, Baltimore. Our first grant from the NIH was awarded in April 2021 and provides for potential funding up to five years totaling approximately $ 0.5 million. In June 2023, we received another grant from the NIH that provides for potential funding up to five years totaling approximately $ 4.6 million. Income from grants is recognized in the period during which the related specified expenses are incurred, provided that the conditions under which the grants were provided have been met. We recognized $ 4.8 million, $ 1.9 million and $ 1.6 million of grant income and recorded the amounts in Other income (expense), net in the consolidated statements of operations during the years ended December 31, 2023 , 2022, and 2021, respectively. A grant receivable of $ 0 and $ 1.0 million representing unreimbursed, eligible costs incurred under the CARB-X agreement was recorded and included in Prepaid expenses and other current assets in the consolidated balance sheets as of December 31, 2023 and 2022, respectively.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Net Loss Per Share	13. Net Loss Per Share The following table sets forth the computation of basic and diluted net loss per share and excludes shares which are legally outstanding, but subject to repurchase by us: Year Ended December 31, 2023 2022 2021 Net loss (in thousands) $ ( 402,266 ) $ ( 223,485 ) $ ( 100,077 ) Weighted-average shares outstanding used in computing net (1) 97,157,690 64,877,988 51,922,108 Net loss per share, basic and diluted $ ( 4.14 ) $ ( 3.44 ) $ ( 1.93 ) ____________________________ (1) Includes shares of common stock into which pre-funded warrants may be exercised. See Note 9, “Pre-Funded Warrants.” The following potentially dilutive securities were excluded from the computation of diluted net loss per share for the period presented because including them would have been antidilutive: Year Ended December 31, 2023 2022 2021 Stock options 9,351,546 7,752,204 5,357,389 Restricted stock units 753,462 456,766 - Employee stock purchase plan 103,628 113,240 66,404 Total 10,208,636 8,322,210 5,423,793

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	14. Income Taxes Our pre-tax book loss was derived from our business operations within the United States. A reconciliation of our effective tax rate to the statutory U.S. federal rate is as follows: Year Ended December 31, 2023 2022 2021 Statutory rate 21.0 % 21.0 % 21.0 % Stock-based compensation 0.5 % 1.5 % 2.2 % Credits 1.4 % 0.8 % 1.1 % Change in valuation allowance ( 21.8 )% ( 21.3 )% ( 23.0 )% Section 162(m) limitation ( 1.1 )% ( 1.8 )% ( 1.1 )% Other 0.0 % ( 0.2 )% ( 0.2 )% Total 0.0 % 0.0 % 0.0 % Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of the assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The following table presents significant components of our deferred tax assets as of December 31, 2023 and 2022: As of December 31, 2023 2022 (in thousands) Deferred tax assets: Net operating losses 135,298 111,555 Fixed assets 660 1,062 Accrued and others 11,279 1,103 R&D Credits 12,870 5,436 Capitalized R&D expenditures 79,485 32,873 Accrued manufacturing expenses 10,819 2,063 Lease liability 8,739 5,358 Intangible assets 29,302 6,867 Stock compensation 8,981 4,474 Total deferred tax assets 297,434 170,791 Deferred tax liabilities: ROU asset ( 9,269 ) ( 6,357 ) Total deferred tax liabilities ( 9,269 ) ( 6,357 ) Net deferred tax asset 288,165 164,433 Valuation allowance ( 288,165 ) ( 164,433 ) Net deferred taxes $ — $ — At December 31, 2023, we have net operating loss (“NOL”) carryforwards of approximately $ 351.9 million and $ 693.6 million available to reduce future taxable income, if any, for federal and state income tax purposes, respectively. The federal and state NOL carryforwards, except the federal loss carryforward arising in tax years beginning after December 31, 2017, begin to expire in 2034 unless previously utilized. Federal NOLs arising in tax years beginning after December 31, 2017 have an indefinite carryover period and do not expire. At December 31, 2023, we have research credit carryforwards of $ 12.8 million and $ 4.6 million available to offset future income tax liabilities, if any, for federal and California income tax purposes, respectively. The federal research and development tax credit carryforwards expire beginning in 2039 unless previously utilized. The California tax credits can be carried forward indefinitely. We have evaluated the positive and negative evidence bearing upon the realizability of our deferred tax assets. Based on our history of operating losses, we have concluded that it is more likely than not that the benefit of our deferred tax assets will not be realized. Accordingly, we have provided a full valuation allowance for deferred tax assets as of December 31, 2023 and 2022. Utilization of the NOL and research credit carryforward may be subject to an annual limitation due to the ownership percentage change limitations under Section 382 and Section 383, respectively, provided by the Internal Revenue Code of 1986, as amended (the “Code”), and similar state provisions. The annual limitation may result in the expiration of the NOL before utilization. We have experienced ownership changes in the past. There were no ownership changes identified in 2023, as such we have determined that no federal research credits will expire unutilized or are excluded from our research credit carryforwards. Subsequent ownership changes may affect the limitation in future years. We have uncertain tax benefits (“UTBs”) totaling $ 4.4 million and $ 1.8 million as of December 31, 2023 and 2022, respectively, which were netted against deferred tax assets subject to valuation allowance. The UTBs had no effect on the effective tax rate. We recognize interest and penalties related to UTBs, when they occur, as a component of income tax expense. To the extent accrued interest and penalties do not ultimately become payable, amounts accrued will be reduced and reflected as a reduction of the provision for income taxes in the period such determination is made. There were no interest or penalties recognized for the years ended December 31, 2023 and 2022. We do not expect our UTBs to change significantly over the next 12 months. A reconciliation of the beginning and ending unrecognized tax benefit amount is as follows: December 31, 2023 2022 2021 (in thousands) Balance at the beginning of the year $ 1,754 $ 924 $ 393 Additions based on tax positions related to current year 2,208 876 461 Additions based on tax positions related to prior years 485 ( 46 ) 70 Balance at end of year $ 4,447 $ 1,754 $ 924 We file U.S. federal and state tax returns. In general, the Company is no longer subject to tax examination by the Internal Revenue Service or state taxing authorities for years before 2019. Although the federal and state statutes are closed for purposes of assessing additional income tax in those prior years, the taxing authorities may still make adjustments to the NOL and credit carryforwards used in open years. Therefore, the tax statutes should be considered open as it relates to the NOL and credit carryforwards used in open years. We do not have any tax audits or other issues pending. In accordance with the 2017 Tax Act, research and experimental (“R&E” ) expenses under Internal Revenue Code Section 174 are required to be capitalized beginning in 2022. R&E expenses are required to be amortized over a period of five years for domestic expenses and 15 years for foreign expenses. The Company has capitalized research and experimental expenditures in its current tax provision as a result. The Inflation Reduction Act of 2022 specifically introduces the topic of corporate alternative minimum tax on adjusted financial statement income on applicable corporations for taxable years beginning after December 31, 2022. There is no impact to the Company’s current tax provision. The American Rescue Plan Act was signed on March 11, 2021. One of the provisions of the Act included expanding the definition of covered employees subject to IRC 162(m) to include an additional top five highest compensated officers beyond the CEO, CFO, and three highest paid employees currently covered under IRC 162(m). This expanded provision is applicable for tax years beginning after December 31, 2026. We do not believe that this update to IRC 162(m) would have a material impact on its income tax provision currently and will continue to monitor this.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Party Transactions	15. Related Party Transactions We have an ongoing relationship with Sutro Biopharma. In 2013, Sutro Biopharma provided support to facilitate the establishment of our Company. As of December 31, 2021 and 2020, Sutro Biopharma owned approximately 1.6 million shares of our common stock. As of December 31, 2019, Sutro Biopharma also owned warrants to purchase 31,857 shares of our common stock (the “Common Stock Warrant”) at an exercise price of $ 0.79289 per share and 59,276 shares of our Series C redeemable convertible stock (the “Preferred Stock Warrant”) at an exercise price of $ 11.5215 per share. The Common Stock Warrant and the Preferred Stock Warrant were automatically net exercised pursuant to their terms for 30,278 shares and 16,591 shares, respectively, of our common stock in connection with our initial public offering in June 2020. In the agreements and amendments identified herein, we licensed certain intellectual property and acquired certain supply rights from Sutro Biopharma, including the right to use the XpressCF platform to discover and develop vaccine candidates for the treatment or prophylaxis of infectious diseases. On October 12, 2015, we and Sutro Biopharma (the “Parties”) entered into the Sutro Biopharma License Agreement, which amended and restated an agreement dated August 1, 2014. The Sutro Biopharma License Agreement was subsequently amended on May 9, 2018 (“License Amendment A1”) and May 29, 2018 (“License Amendment A2”). In consideration for the License Amendment A2, we issued to Sutro Biopharma the Preferred Stock Warrant to purchase 59,276 shares of Series C redeemable convertible preferred stock at a purchase price of $ 11.5215 per share. We also entered into a separate supply agreement with Sutro Biopharma on May 29, 2018 (the “Sutro Biopharma Supply Agreement”). As of June 2, 2021, Sutro Biopharma was no longer considered a related party. Under the Sutro Biopharma License Agreement, Sutro Biopharma granted us an exclusive, worldwide license to research, develop, manufacture and commercialize vaccine products addressing infectious disease, which are discovered or produced based on the use of Sutro Biopharma’s proprietary cell-free protein expression technology, known as XpressCF, which utilizes extracts derived from strains of E. coli . In connection with the Sutro Biopharma License Agreement, under the Sutro Biopharma Supply Agreement, Sutro Biopharma has agreed to manufacture and supply extracts and reagents for us on a cost-plus basis. In consideration for the rights licensed, we are obligated to pay a 4 % royalty on worldwide aggregate annual net sales of our vaccine products for human health and a 2 % royalty on annual net sales of vaccine products for animal health. In License Amendment A1, the Parties amended the license agreement to remove a pre-IND regulatory meeting as a diligence milestone and to agree that certain other diligence milestones had been satisfied. In License Amendment A2, the Parties amended the license agreement to add certain terms confirming our obligation to purchase Sutro Biopharma’s proprietary extract from E. coli (“Extract”) from Sutro Biopharma. In addition, the Parties amended the license agreement to specify our rights to a transfer of certain know-how relating to the manufacture of Extract in the event of a declaration of bankruptcy by Sutro Biopharma. Finally, the Parties agreed to terms providing for injunctive relief in the event of a breach or threatened breach by the other party. In the Sutro Biopharma Supply Agreement, the Parties agreed to terms for the supply of manufactured Extract and custom reagents by Sutro Biopharma for us to use in manufacturing vaccine compositions in non-clinical research or in Phase 1 or Phase 2 clinical trials. The term of the Sutro Biopharma Supply Agreement is from execution until the later of July 31, 2021 and the date the parties enter into and commence activities under the supply agreement unless extended through a subsequent supply agreement for the supply of Extract and custom reagents for vaccine compositions for Phase 3 and commercial uses as contemplated in the Supply Agreement. In February 2021, we entered into an amendment to the Sutro Biopharma Supply Agreement and extended the term to July 31, 2022. As Sutro Biopharma was no longer considered a related party as of June 2, 2021, we excluded expenses after that date from related party transaction expenses. We recognized expense related to the Supply Agreement of $ 0 million, $ 0 million and $ 2.4 million for the years ended December 31, 2023, 2022 and 2021, respectively.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	16. Subsequent Events On February 2, 2024, we completed an underwritten public offering of 12,695,312 shares of our common stock, which included the full exercise of the underwriters’ option to purchase an additional 1,757,812 shares, at a price of $ 64.00 per share and pre-funded warrants to purchase 781,250 shares of our common stock at a price of $ 63.999 per underlying share. In aggregate, we received $ 816.5 million in net proceeds after deducting underwriting discounts and commissions and other estimated offering expenses payable by us, and excluding the exercise of any pre-funded warrants.

Basis of Presentation and Sum_2

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation These consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (the “SEC”) regarding annual reporting. The consolidated financial statements include the Company and its wholly owned subsidiary. All intercompany transactions and balances have been eliminated upon consolidation.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and expenses and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements. On an ongoing basis, we evaluate our estimates and assumptions, including those related to stock-based compensation expense, accruals for certain research and development costs, the incremental borrowing rate, the valuation of deferred tax assets and income taxes. Management bases our estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ materially from those estimates.
Concentration of Credit Risk and Other Risks and Uncertainties	Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that potentially subject us to a concentration of credit risk consist primarily of cash, cash equivalents and investments. We invest in money market funds, U.S. Treasury securities, U.S. government agency securities, corporate debt, commercial paper and asset-backed securities. We maintain bank deposits in federally insured financial institutions and these deposits may exceed federally insured limits. We are exposed to credit risk in the event of a default by the financial institutions holding our cash and issuers of investments to the extent recorded on the consolidated balance sheets. For example, on March 10, 2023, the California Department of Financial Protection and Innovation took control of Silicon Valley Bank (“SVB”) and appointed the Federal Deposit Insurance Corporation (“FDIC”) as receiver. While SVB was our primary bank at the time, we maintained banking relationships with other major banks. The substantial majority of funds we held at SVB, which included cash, cash equivalents and investments, were held in custodial accounts of a third-party institution for which SVB Asset Management was the advisor (“SVB Custodial Accounts”). On March 12, 2023, the FDIC confirmed that depositors of SVB would have access to all of their money and, as a result, we regained access to all of our funds deposited with SVB. The FDIC subsequently transferred SVB’s deposits and loans to a newly created bridge bank, named Silicon Valley Bridge Bank, N.A. (“Silicon Valley Bridge Bank”). On March 26, 2023, the FDIC announced that First Citizens Bank & Trust Company (“First Citizens Bank”) had agreed to purchase and assume all deposits and loans of Silicon Valley Bridge Bank. We have not experienced any losses on these deposits or investments as a result of this market event. While we were able to recover all deposited amounts from SVB, and continue to have access to all investments held in the SVB Custodial Accounts, there can be no assurance that our current or future banks will not face similar risks as SVB or that we will be able to recover in full our deposits in the event of similar closures. Our investment policy limits investments to money market funds, certain types of debt securities issued by the U.S. Government and its agencies, corporate debt, commercial paper and asset-backed securities, and places restrictions on the credit ratings, maturities and concentration by type and issuer. We have not experienced any significant losses on our deposits of cash, cash equivalents or investments. We are subject to supplier concentration risk from certain vendors. Although we are working to establish secondary sources of supply, we currently source several of our critical raw materials from single-source suppliers. We also use one contract manufacturing organization (“CMO”), Lonza Ltd. (“Lonza”), to handle most of our manufacturing activities for our VAX-24 and VAX-31 programs. If we were to experience disruptions in raw materials supplied by our suppliers, or in manufacturing activities at Lonza, we may experience significant delays in our product development timelines and may incur substantial costs to secure alternative sources of raw materials or manufacturing. Our future results of operations involve a number of other risks and uncertainties. Factors that could affect our future operating results and cause actual results to vary materially from expectations include, but are not limited to: our early stages of clinical vaccine development; our ability to advance vaccine candidates into, and successfully complete, clinical trials on the timelines we project; our ability to adequately demonstrate sufficient safety and immunogenicity or efficacy of our vaccine candidates; our ability to enroll subjects in our ongoing and future clinical trials; our ability to successfully manufacture and supply our vaccine candidates for clinical trials or for future potential commercialization; our ability to obtain additional capital to finance our operations; our ability to obtain, maintain and protect our intellectual proper ty rights; developments relating to our competitors and our industry, including competing vaccine candidates; general and market conditions; and other risks and uncertainties, including those more fully described in the “Risk Factors” section of this Annual Report on Form 10-K.
Segment and Geographical Information	Segment and Geographical Information We operate and manage our business as one reportable and operating segment. Our chief executive officer, who is the chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. Most of our long-lived assets are based in the United States. Long-lived assets are comprised of property and equipment.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash We consider all highly liquid investments purchased with original maturities of three months or less from the date of purchase to be cash equivalents. Cash equivalents consist primarily of amounts invested in money market funds and commercial paper and are stated at their fair values. Restricted cash consists of two standby letters of credit that serve as collateral for the lease agreements for our current corporate headquarters. Cash, cash equivalents and restricted cash as reported within the consolidated statements of cash flows consisted of the following: Years Ended December 31, 2023 2022 (in thousands) Cash and cash equivalents $ 397,451 $ 834,657 Restricted cash 1,103 871 Cash, cash equivalents and restricted cash $ 398,554 $ 835,528
Investments	Investments Our investments have been classified and accounted for as available-for-sale securities. Fixed income securities consist of U.S. Treasury securities, U.S. government agency securities, corporate debt, commercial paper and asset-backed securities. These securities are recorded on the consolidated balance sheets at fair value. Unrealized gains and losses on these securities are included as a separate component of accumulated other comprehensive gain (loss). The cost of investment securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion are included in other income (expense), net. Realized gains and losses are also included in other income (expense), net. When the fair value of a debt security declines below its amortized cost basis, any portion of that decline attributable to credit losses, to the extent expected to be nonrecoverable before the sale of the security, is recognized in our consolidated statements of operations. When the fair value of a debt security declines below its amortized cost basis due to changes in interest rates, such amounts are recorded in other comprehensive loss, and are recognized in our consolidated statements of operations only if we sell or intend to sell the security before recovery of its cost basis.
Property and Equipment, Net	Property and Equipment, Net Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally three to five years . Leasehold improvements are amortized over the shorter of the expected life or lease term. Repairs and maintenance expenditures, which are not considered improvements and do not extend the useful life of property and equipment, are expensed as incurred. When assets are retired or otherwise disposed of, the cost and related accumulated depreciation and amortization are removed from the consolidated balance sheets and the resulting gain or loss is reflected in the consolidated statements of operations in the period realized.
Leases	Leases We determine if an arrangement is a lease at inception. In addition, we determine whether a lease meets the classification criteria of a finance or operating lease at the lease commencement date considering whether: (i) the lease transfers ownership of the underlying asset to the lessee at the end of the lease term; (ii) the lease grants the lessee an option to purchase the underlying asset that the lessee is reasonably certain to exercise; (iii) the lease term is for a major part of the remaining economic life of the underlying asset; (iv) the present value of the sum of the lease payments and residual value guaranteed by the lessee equals or exceeds substantially all of the fair value of the underlying asset; and (v) the underlying asset is such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease term. As of December 31, 2023 and 2022, our lease population consisted of real estate operating leases and we did no t have any finance leases. Operating leases are included in Operating lease right-of-use (“ROU”) assets, Operating lease liabilities — current and Operating lease liabilities — long term in our consolidated balance sheets. ROU assets represent our right to use the underlying assets for the lease term and lease liabilities represent our obligation to make lease payments arising from the leases. Operating lease ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. In determining the present value of lease payments, if the rate implicit in the lease is not readily determinable, we use our incremental borrowing rate based on the information available at the lease commencement date. We determine the incremental borrowing rate based on an analysis of corporate bond yields with a credit rating similar to ours. The determination of our incremental borrowing rate requires management judgment, including development of a synthetic credit rating and cost of debt, as we currently do not carry any debt. We believe that the estimates used in determining the incremental borrowing rate are reasonable based upon current facts and circumstances. Applying different judgment to the same facts and circumstances could yield a different incremental borrowing rate. The operating lease ROU assets also include adjustments for prepayments and accrued lease payments and exclude lease incentives. ROU assets and lease liabilities may include options to extend or terminate leases if it is reasonably certain that we will exercise such options. Lease payments which are fixed and determinable are amortized as rent expense on a straight-line basis over the expected lease term. Variable lease costs, which are dependent on usage, a rate or index, including common area maintenance charges, are expensed as incurred. Lease agreements that include lease and non-lease components are accounted for as a single lease component. Lease agreements with non-cancelable terms of less than 12 months are not recorded on our consolidated balance sheets.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets We review long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparing the carrying amount to the future undiscounted net cash flows which the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recogni zed is measured as the amount by which the carrying amount of the assets exceeds the projected discounted future net cash flows generated by the assets. There were $ 0 million, $ 0.2 and $ 0 million of impairments of long-lived assets during the years ended December 31, 2023 , 2022 and 2021, respectively.
Fair Value Measurements	Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. The carrying amounts of our financial instruments, including cash and cash equivalents, prepaid and other current assets, accounts payable, accrued expenses, and other liabilities, approximate fair value due to their short-term maturities.
Research and Development	Research and Development Research and development costs are expensed as incurred. Research and development costs include salaries, stock-based compensation and benefits for employees performing research and development activities, an allocation of facility and overhead expenses, expenses incurred under agreements with consultants, CMOs, contract research organizations (“CROs”) and investigative sites that conduct preclinical studies, clinical trials other supplies and costs associated with product development efforts, preclinical activities, clinical trials and regulatory operations.
Accrued Research and Development	Accrued Research and Development We have entered into various agreements with CROs and CMOs. Our research and development accruals, which include accrued manufacturing expenses, are estimated based on the level of services performed, progress of the studies, including the phase or completion of events, and contracted costs. The estimated costs of research and development services provided, but not yet invoiced, are included in accrued expenses on the consolidated balance sheets. If the actual timing of the performance of services or the level of effort varies from the original estimates, we adjust the accrual accordingly. Payments made to CROs or CMOs under these arrangements in advance of the performance of the related services are recorded as prepaid expenses and other current assets until the services are rendered. To date, there have been no material differences between our estimates of such expenses and the amounts actually incurred.
Option to Acquire Manufacturing Rights	Acquired Manufacturing Rights In December 2022, we entered into an option agreement with Sutro Biopharma (the “Option Agreement”). The Option Agreement we acquired, among other things, a right, but not an obligation, to obtain certain exclusive rights to internally manufacture and/or source extract from certain CMOs and the right to independently develop and make improvements to the extract for use in connection with the exploitation of certain vaccine compositions (the “Option”). As consideration for the Option and other rights and authorizations granted to us under the Option Agreement, we paid Sutro Biopharma upfront consideration. In September 2023, we and Sutro Biopharma mutually agreed in writing to the Form Definitive Agreement (as defined below) to become effective in the event we exercised the Option, and paid Sutro Biopharma the amount due upon mutual agreement of the Form Definitive Agreement. In November 2023, we exercised the Option and paid the Option exercise price and accrued the remaining payment we are obligated to pay Sutro Biopharma. As of December 31, 2022 and 2023, we have determined there is no current alternative future use of the acquired manufacturing rights paid and expensed the Option as of December 31, 2022 and 2023. We have classified such costs incurred related to the execution of the Option Agreement, the mutual agreement of the Form Definitive Agreement and the Option exercise, as Acquired Manufacturing Rights on the accompanying consolidated statements of operations for the years ended December 31, 2022 and 2023, respectively. See Note 7, “Commitments and Contingencies, Sutro Option Agreement,” for further details.
Income Taxes	Income Taxes We account for income taxes using the asset and liability method. We recognize deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the consolidated financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the consolidated financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. In evaluating the ability to recover our deferred income tax assets, we consider all available positive and negative evidence, including our operating results, ongoing tax planning and forecasts of future taxable income on a jurisdiction-by-jurisdiction basis. In the event we determine that we would be able to realize our deferred income tax assets in the future in excess of their net recorded amount, we would make an adjustment to the valuation allowance that would reduce the provision for income taxes. Conversely, in the event that all or part of the net deferred tax assets are determined not to be realizable in the future, an adjustment to the valuation allowance would be charged to earnings in the period when such determination is made. As of December 31, 2023 and 2022, we have recorded a full valuation allowance on our deferred tax assets. Tax benefits related to uncertain tax positions are recognized when it is more likely than not that a tax position will be sustained during an audit. Interest and penalties related to unrecognized tax benefits are included within the provision for income tax.
Stock-Based Compensation Expense	Stock-Based Compensation Expense For options granted to employees, non-employees and directors, stock-based compensation is measured at grant date based on the fair value of the award. We determine the grant-date fair value of the options using the Black-Scholes option-pricing model. The fair value of restricted stock and restricted stock unit (“RSU”) awards is determined based on the number of units granted and the closing price of the Company’s common stock as of the grant-date. The grant-date fair value of awards is amortized over the employees’ requisite service period or the non-employees’ vesting period as the services are rendered. Forfeitures are accounted for as they occur. Additionally, our 2020 Employee Stock Purchase Plan is deemed to be a compensatory plan and is therefore included in stock-based compensation expense.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes net loss and other comprehensive loss for the period. Other comprehensive loss consists of unrealized loss on investments and foreign currency translation adjustments, net.
Foreign Currency Transactions	Foreign Currency Transactions Transactions denominated in foreign currencies are initially measured in U.S. dollars using the exchange rate on the date of the transaction. Foreign currency denominated monetary assets and liabilities are subsequently re-measured at the end of each reporting period using the exchange rate at that date, with the corresponding foreign currency transaction gain or loss recorded in the consolidated statements of operations and consolidated statements of cash flows. Nonmonetary assets and liabilities are not subsequently re-measured. For our international operations, local currencies have been determined to be the functional currencies. We translate functional currency assets and liabilities to their U.S. dollar equivalents at exchange rates in effect as of the balance sheet date and income and expense amounts at average exchange rates for the period. Gains and losses from foreign currency translation are included in accumulated other comprehensive loss within stockholders’ equity in the consolidated balance sheets.
Net Loss Per Share	Net Loss Per Share Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common stock outstanding, including pre-funded warrants, during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, common stock subject to repurchase, and stock options are considered to be potentially dilutive securities. Shares of common stock into which the pre-funded warrants may be exercised are considered outstanding for the purposes of computing net loss per share because the shares may be issued for little consideration, are fully vested and are exercisable after the original issuance date. Basic and diluted net loss attributable to common stockholders per share is presented in conformity with the two-class method required for participating securities as the redeemable convertible preferred stock is considered a participating security. Our participating securities do not have a contractual obligation to share in our losses. As such, the net loss was attributed entirely to common stockholders. Because we have reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods.
Recently Issued Accounting Standards Not Yet Adopted	Recently Issued Accounting Standards Not Yet Adopted From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies and adopted by us as of the specified effective date. We believe that the impact of recently issued standards that are not yet effective will not have a material impact on our consolidated financial statements and disclosures. In November 2023, the FASB issued Accounting Standards Update (“ASU”) No. 2023-07: Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. The ASU requires entities to report incremental information about significant segment expenses included in a segment’s profit or loss measure as well as the name and title of the chief operating decision maker. The guidance also requires interim disclosures related to reportable segment profit or loss and assets that had previously only been disclosed annually. This guidance is effective for annual periods beginning after December 15, 2024. We are currently evaluating the impact of the new guidance on the disclosures to our consolidated financial statements. In December 2023, the FASB issued ASU No. 2023-09: Income Taxes (Topic 740): Improvements to Income Tax Disclosures. The ASU improves the transparency of income tax disclosures by requiring (i) consistent categories and greater disaggregation of information in the rate reconciliation and (ii) income taxes paid disaggregated by jurisdiction. This guidance is effective for fiscal years beginning after December 15, 2024 on a prospective basis and retrospective application is permitted. We are currently evaluating the impact of the new guidance on the disclosures to our consolidated financial statements.

Basis of Presentation and Sum_3

Basis of Presentation and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Schedule of Cash, Cash Equivalents And Restricted Cash	Cash, cash equivalents and restricted cash as reported within the consolidated statements of cash flows consisted of the following: Years Ended December 31, 2023 2022 (in thousands) Cash and cash equivalents $ 397,451 $ 834,657 Restricted cash 1,103 871 Cash, cash equivalents and restricted cash $ 398,554 $ 835,528

Fair Value Measurements and F_2

Fair Value Measurements and Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Schedule of Financial Instruments Measured at Fair Value on Recurring Basis	The following tables set forth our financial instruments measured at fair value on a recurring basis by level within the fair value hierarchy at December 31, 2023 and 2022: December 31, 2023 Fair Value Amortized Gross Gross Fair Assets (in thousands) Cash and cash equivalents: Cash Level 1 $ 50,003 $ — $ — $ 50,003 Money market funds Level 1 47,357 — — 47,357 Commercial paper Level 2 300,256 — ( 165 ) 300,091 Total cash and cash equivalents 397,616 — ( 165 ) 397,451 Investments: U.S. Treasury securities Level 1 481,704 422 ( 44 ) 482,082 Commercial paper Level 2 102,435 7 ( 35 ) 102,407 Corporate debt Level 2 133,523 168 ( 42 ) 133,649 Asset backed securities Level 2 23,963 18 — 23,981 U.S. government agency securities Level 2 103,484 — ( 152 ) 103,332 Total investments 845,109 615 ( 273 ) 845,451 Total assets measured at fair value $ 1,242,725 $ 615 $ ( 438 ) $ 1,242,902 December 31, 2022 Fair Value Amortized Gross Gross Fair Assets (in thousands) Cash and cash equivalents: Cash Level 1 $ 56,198 $ — $ — $ 56,198 Money market funds Level 1 680,934 — — 680,934 Commercial paper Level 2 92,581 — ( 34 ) 92,547 U.S. government agency securities Level 2 4,978 — — 4,978 Total cash and cash equivalents 834,691 — ( 34 ) 834,657 Investments: U.S. Treasury securities Level 1 37,651 — ( 70 ) 37,581 Commercial paper Level 2 28,161 — ( 17 ) 28,144 Corporate debt Level 2 25,402 — ( 131 ) 25,271 Asset backed securities Level 2 6,954 20 — 6,974 U.S. government agency securities Level 2 25,427 19 ( 148 ) 25,298 Total investments 123,595 39 ( 366 ) 123,268 Total assets measured at fair value $ 958,286 $ 39 $ ( 400 ) $ 957,925
Schedule of Contractual Maturities of Investments	The following table presents the contractual maturities of our investments as of December 31, 2023 (in thousands): December 31, 2023 Fair Value Due in less than one year $ 682,776 Due in one to five years 162,675 Total $ 845,451

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets as of December 31, 2023 and 2022 consisted of the following: December 31, December 31, 2023 2022 (in thousands) Prepaid expenses $ 6,159 $ 5,312 Purchased equipment deposits 3,856 — Interest receivable 3,598 2,848 Grant receivable 9 1,029 Other current assets 2,105 1,990 Total $ 15,727 $ 11,179
Schedule of Property and Equipment, Net	Property and equipment, net as of December 31, 2023 and 2022 consisted of the following: December 31, 2023 2022 (in thousands) Furniture and equipment $ 1,608 $ 1,608 Computers and computer software 771 416 Lab equipment 25,110 13,100 Leasehold improvements 1,460 1,353 Manufacturing equipment and auxiliary 8,134 — Manufacturing facility and equipment construction-in-progress (1) 51,815 — Total property and equipment 88,898 16,477 Less: accumulated depreciation and amortization ( 9,272 ) ( 6,117 ) Property and equipment, net $ 79,626 $ 10,360 ____________ (1) See Note 4, “ Commercial Manufacturing and Supply Agreement, ” for further details.
Summary of Other Assets	Other assets as of December 31, 2023 and 2022 consisted of the following: December 31, December 31, 2023 2022 (in thousands) Manufacturing facility construction buildout (1) $ 34,688 $ — Long-term prepaid assets 2,768 4,361 Other long-term assets 106 194 Total $ 37,562 $ 4,555 _____________ (1) See Note 4, “ Commercial Manufacturing and Supply Agreement, ” for further details.
Schedule of Accrued Expenses	Accrued expenses as of December 31, 2023 and 2022 consisted of the following: December 31, 2023 2022 (2) (in thousands) Clinical studies $ 2,156 $ 1,518 Other research and development 30,759 7,446 Acquired manufacturing rights (1) 25,000 5,000 Other accrued expenses 1,900 1,411 Total $ 59,815 $ 15,375 ______________ (1) See Note 7, “ Commitments and Contingencies, Sutro Option Agreement, ” for further details. (2) The breakout and categorizations of the 2022 total accrued expenses have been updated to conform to the 2023 presentation.

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Schedule of Information Related to ROU Assets and Lease Liabilities	Information related to our ROU assets and related lease liabilities was as follows (dollar amounts in thousands): December 31, December 31, 2023 2022 Cash paid for operating lease liabilities $ 7,390 $ 5,374 Operating lease right-of-use assets $ 30,997 $ 21,288 Operating lease liabilities - current $ 7,113 $ 5,910 Operating lease liabilities - long-term 22,111 12,031 Total lease liabilities $ 29,224 $ 17,941 Weighted-average remaining lease term (in years) 5.71 2.78 Weighted-average discount rate 8.4 % 7.6 %
Schedule of Maturities of Lease Liabilities	Maturities of lease liabilities as of December 31, 2023 were as follows: Years ending December 31, (in thousands) 2024 $ 8,817 2025 9,836 2026 2,899 2027 2,986 2028 3,075 Thereafter 9,503 Total future undiscounted lease payments 37,115 Less: Imputed interest ( 7,891 ) Total lease liabilities $ 29,224

Commitments and Contingencies (

Commitments and Contingencies (Table)	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Schedule of Non-cancelable Purchase Commitments Related to Raw Materials	As of December 31, 2023, we had the following amounts of non-cancelable purchase commitments related to manufacturing services and raw materials purchased due to our key manufacturing partners. These amounts represent our minimum contractual obligations, including termination fees. If we terminate certain firm orders with key manufacturing partners, we will be required to pay for the manufacturing services scheduled or raw materials purchased under our arrangements. The actual amounts we pay in the future to our vendors under such agreements may differ from the purchase order amounts. Years ending December 31, (in thousands) 2024 $ 181,812 2025 41,840 2026 1,296 2027 414 Total non-cancelable purchase commitments due to key manufacturing partners $ 225,362

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Schedule of Common Stock Shares Reserved for Future Issuance	Common stock reserved for future issuances under the 2020 Equity Incentive Plan (the “2020 Plan”) and the 2014 Equity Incentive Plan (the “2014 Plan”) was as follows, and excludes 36,710 shares issued outside of the 2014 Plan and 2020 Plan: December 31, December 31, 2023 2022 Options issued and outstanding 9,314,836 7,715,494 Restricted stock units issued and outstanding 753,462 456,766 Shares available for future stock option grants 6,065,150 4,679,598 Total 16,133,448 12,851,858

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2023
Nonvested Restricted Stock Shares Activity	RSU activity for the years ended December 31, 2023 and 2022 was as follows: Shares Weighted- Unvested at December 31, 2021 — $ — Granted 581,047 26.25 Vested and released ( 79,229 ) 24.79 Cancelled ( 45,052 ) 24.32 Unvested at December 31, 2022 456,766 $ 26.70 Granted 574,123 45.57 Vested and released ( 232,890 ) 30.97 Cancelled ( 44,537 ) 40.78 Unvested at December 31, 2023 753,462 $ 38.93
Summary of Activity under Employee Stock Purchase Plan	Activity under our 2020 ESPP was as follows: Shares Balance - December 31, 2021 1,070,704 Additional shares authorized 530,319 Shares purchased ( 61,709 ) Balance - December 31, 2022 1,539,314 Additional shares authorized 794,706 Shares purchased ( 76,275 ) Balance - December 31, 2023 2,257,745
Summary of Estimated Fair Value of Employee Stock Options	We estimated the fair value of employee stock options using the Black-Scholes option-pricing model for the years ended December 31, 2023, 2022 and 2021 using the following weighted-average assumptions: Year Ended December 31, 2023 2022 2021 Fair Value Assumptions Expected volatility 71.3 % - 74.0 % 78.1 % - 85.1 % 81.0 % - 84.1 % Expected dividend yield 0 % 0 % 0 % Expected term (in years) 5.3 - 5.4 5.3 - 5.5 5.3 - 5.5 Risk-free interest rate 3.5 % - 4.6 % 1.6 % - 4.4 % 0.5 % - 1.3 %
2020 Plan and 2014 Plan
Summary of Activity Under Stock Option Plans	Stock option activity under our 2020 Plan and 2014 Plan, which excludes options to purchase 36,710 shares granted outside of the 2020 Plan and 2014 Plan, was as follows: Options Outstanding Stock Option and Restricted Stock Units Activity Options Number Weighted- Weighted- Aggregate Balances — December 31, 2021 6,104,756 5,295,007 $ 9.30 Additional shares authorized 2,651,598 — Options granted ( 3,850,981 ) 3,850,981 $ 27.67 Options exercised 385 (1) ( 1,153,285 ) $ 4.25 Options forfeited 277,209 ( 277,209 ) $ 23.54 Restricted Stock Units granted ( 581,047 ) Restricted Stock Units withheld 32,626 Restricted Stock Units forfeited 45,052 Balances — December 31, 2022 4,679,598 7,715,494 $ 18.70 8.20 $ 225,667 Additional shares authorized 3,973,533 Options granted ( 2,343,037 ) 2,343,037 $ 44.44 Options exercised 1,080 (1) ( 538,888 ) $ 10.50 Options forfeited 204,807 ( 204,807 ) $ 32.58 Restricted Stock Units granted ( 574,123 ) Restricted Stock Units withheld 78,755 Restricted Stock Units forfeited 44,537 Balances — December 31, 2023 6,065,150 9,314,836 $ 25.35 7.75 $ 348,868 Vested and expected to vest — December 31, 2023 9,314,836 $ 25.35 7.75 $ 348,868 Exercisable at December 31, 2023 4,646,989 $ 16.40 6.80 $ 215,608 ______________________________________ (1) Shares returned due to net exercises .
2020 Employee Stock Purchase Plan
Summary of Estimated Fair Value of Shares Under Employee Stock Purchase Plan	We estimated the fair value of shares under the 2020 ESPP using the Black-Scholes option-pricing model for the years ended December 31, 2023, 2022 and 2021 using the following weighted-average assumptions: Year Ended December 31, 2023 2022 2021 Fair Value Assumptions Expected volatility 38.1 % - 99.7 % 78.8 % - 99.7 % 79.6 % - 126.3 % Expected dividend yield 0 % 0 % 0 % Expected term (in years) 0.5 - 2.0 0.5 - 2.0 0.5 - 2.0 Risk-free interest rate 4.2 % - 5.4 % 0.1 % - 4.7 % 0.0 % - 0.5 %
2014 Plan, 2020 Plan and 2020 ESPP
Summary of Stock-based Compensation Expense	We recorded total stock-based compensation expense for the years ended December 31, 2023, 2022 and 2021 related to the 2014 Plan, the 2020 Plan and the 2020 ESPP in the consolidated statements of operations and allocated the amounts as follows: Year Ended December 31, 2023 2022 2021 (In thousands) Research and development $ 23,275 $ 9,899 $ 3,954 General and administrative 25,485 13,751 6,775 Total $ 48,760 $ 23,650 $ 10,729

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Net Loss Per Share	The following table sets forth the computation of basic and diluted net loss per share and excludes shares which are legally outstanding, but subject to repurchase by us: Year Ended December 31, 2023 2022 2021 Net loss (in thousands) $ ( 402,266 ) $ ( 223,485 ) $ ( 100,077 ) Weighted-average shares outstanding used in computing net (1) 97,157,690 64,877,988 51,922,108 Net loss per share, basic and diluted $ ( 4.14 ) $ ( 3.44 ) $ ( 1.93 ) ____________________________ (1) Includes shares of common stock into which pre-funded warrants may be exercised. See Note 9, “Pre-Funded Warrants.”
Schedule of Potentially Dilutive Securities Excluded From Computation of Diluted Net Loss Per Share	The following potentially dilutive securities were excluded from the computation of diluted net loss per share for the period presented because including them would have been antidilutive: Year Ended December 31, 2023 2022 2021 Stock options 9,351,546 7,752,204 5,357,389 Restricted stock units 753,462 456,766 - Employee stock purchase plan 103,628 113,240 66,404 Total 10,208,636 8,322,210 5,423,793

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Reconciliation of Effective Tax Rate	A reconciliation of our effective tax rate to the statutory U.S. federal rate is as follows: Year Ended December 31, 2023 2022 2021 Statutory rate 21.0 % 21.0 % 21.0 % Stock-based compensation 0.5 % 1.5 % 2.2 % Credits 1.4 % 0.8 % 1.1 % Change in valuation allowance ( 21.8 )% ( 21.3 )% ( 23.0 )% Section 162(m) limitation ( 1.1 )% ( 1.8 )% ( 1.1 )% Other 0.0 % ( 0.2 )% ( 0.2 )% Total 0.0 % 0.0 % 0.0 %
Components of Deferred Tax Assets	The following table presents significant components of our deferred tax assets as of December 31, 2023 and 2022: As of December 31, 2023 2022 (in thousands) Deferred tax assets: Net operating losses 135,298 111,555 Fixed assets 660 1,062 Accrued and others 11,279 1,103 R&D Credits 12,870 5,436 Capitalized R&D expenditures 79,485 32,873 Accrued manufacturing expenses 10,819 2,063 Lease liability 8,739 5,358 Intangible assets 29,302 6,867 Stock compensation 8,981 4,474 Total deferred tax assets 297,434 170,791 Deferred tax liabilities: ROU asset ( 9,269 ) ( 6,357 ) Total deferred tax liabilities ( 9,269 ) ( 6,357 ) Net deferred tax asset 288,165 164,433 Valuation allowance ( 288,165 ) ( 164,433 ) Net deferred taxes $ — $ —
Reconciliation of Unrecognized Tax Benefit	A reconciliation of the beginning and ending unrecognized tax benefit amount is as follows: December 31, 2023 2022 2021 (in thousands) Balance at the beginning of the year $ 1,754 $ 924 $ 393 Additions based on tax positions related to current year 2,208 876 461 Additions based on tax positions related to prior years 485 ( 46 ) 70 Balance at end of year $ 4,447 $ 1,754 $ 924

Basis of Presentation and Sum_4

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) Segment Lease	Dec. 31, 2022 USD ($) Lease	Dec. 31, 2021 USD ($)
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Number of reportable segments | Segment	1
Number of operating segments | Segment	1
Number of finance lease | Lease	0	0
Asset impairment charges	$ 0	$ 213	$ 0
ROU assets	30,997	21,288
Lease liabilities	$ 29,224	$ 17,941
Minimum
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Estimated useful lives of assets	3 years
Maximum
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Estimated useful lives of assets	5 years

Basis of Presentation and Sum_5

Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Cash, Cash Equivalents And Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Cash and cash equivalents	$ 397,451	$ 834,657
Restricted Cash	1,103	871
Cash, cash equivalents and restricted cash	$ 398,554	$ 835,528	$ 69,856	$ 386,200

Fair Value Measurements and F_3

Fair Value Measurements and Fair Value of Financial Instruments - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) Security	Dec. 31, 2022 USD ($) Security
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Fair value assets transferred into level 3 | $	$ 0	$ 0
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Number of securities | Security	0	0

Fair Value Measurements and F_4

Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Financial Instruments Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Assets:
Investments, Fair Value	$ 845,451
Fair Value, Recurring
Assets:
Cash and cash equivalents, Amortized Cost	397,616	$ 834,691
Cash and cash equivalents, Gross Unrealized Losses	(165)	(34)
Cash and cash equivalents, Fair Value	397,451	834,657
Investments, Amortized Cost	845,109	123,595
Investments, Gross Unrealized Gains	615	39
Investments, Gross Unrealized Losses	(273)	(366)
Investments, Fair Value	845,451	123,268
Total assets measured at fair value, Amortized Cost	1,242,725	958,286
Total assets measured at fair value, Gross Unrealized Gains	615	39
Total assets measured at fair value, Gross Unrealized Losses	(438)	(400)
Total assets measured at fair value, Fair Value	1,242,902	957,925
Fair Value, Recurring | Cash | Level 1
Assets:
Cash and cash equivalents, Amortized Cost	50,003	56,198
Cash and cash equivalents, Fair Value	50,003	56,198
Fair Value, Recurring | Money Market Funds | Level 1
Assets:
Cash and cash equivalents, Amortized Cost	47,357	680,934
Cash and cash equivalents, Fair Value	47,357	680,934
Fair Value, Recurring | Commercial Paper | Level 2
Assets:
Cash and cash equivalents, Amortized Cost	300,256	92,581
Cash and cash equivalents, Gross Unrealized Losses	(165)	(34)
Cash and cash equivalents, Fair Value	300,091	92,547
Fair Value, Recurring | U.S. Treasury Securities | Level 1
Assets:
Investments, Amortized Cost	481,704	37,651
Investments, Gross Unrealized Gains	422
Investments, Gross Unrealized Losses	(44)	(70)
Investments, Fair Value	482,082	37,581
Fair Value, Recurring | Commercial paper | Level 2
Assets:
Investments, Amortized Cost	102,435	28,161
Investments, Gross Unrealized Gains	7
Investments, Gross Unrealized Losses	(35)	(17)
Investments, Fair Value	102,407	28,144
Fair Value, Recurring | Corporate Debt | Level 2
Assets:
Investments, Amortized Cost	133,523	25,402
Investments, Gross Unrealized Gains	168
Investments, Gross Unrealized Losses	(42)	(131)
Investments, Fair Value	133,649	25,271
Fair Value, Recurring | Asset backed securities | Level 2
Assets:
Investments, Amortized Cost	23,963	6,954
Investments, Gross Unrealized Gains	18	20
Investments, Fair Value	23,981	6,974
Fair Value, Recurring | U.S. Government Agency Securities | Level 2
Assets:
Cash and cash equivalents, Amortized Cost		4,978
Cash and cash equivalents, Fair Value		4,978
Investments, Amortized Cost	103,484	25,427
Investments, Gross Unrealized Gains		19
Investments, Gross Unrealized Losses	(152)	(148)
Investments, Fair Value	$ 103,332	$ 25,298

Fair Value Measurements and F_5

Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Contractual Maturities of Investments (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Fair Value Disclosures [Abstract]
Due in less than one year	$ 682,776
Due in one to five years	162,675
Total	$ 845,451

Commercial Manufacturing and _2

Commercial Manufacturing and Supply Agreement - Additional Information (Details) - USD ($)	Oct. 13, 2023	Dec. 31, 2023
Supply Commitment [Line Items]
Automatic renewal period	3 years
Lonza Commercial Manufacturing and Supply Agreement [Member]
Supply Commitment [Line Items]
Agreement expiration date	Dec. 31, 2038
Agreement Termination Description	In the event that Vaxcyte GmbH terminates the agreement for convenience, or Lonza terminates the agreement in the event that Vaxcyte GmbH commits certain specified material breaches, then certain termination consequences may be triggered, including that (i) Vaxcyte GmbH would forfeit any outstanding entitlement to credit from Lonza of the Repurposing Fee (as defined below), and (ii) Vaxcyte GmbH would be obligated to pay Lonza a termination penalty equal to the greater of (a) CHF 70,000,000, or (b) a prespecified number of months’ FTE fees for the actual FTEs assigned to Vaxcyte GmbH as of the date of termination. Within 30 days of the Effective Date, Vaxcyte GmbH paid Lonza a repurposing fee (the “Repurposing Fee”) of CHF 27,000,000 that will be credited back to Vaxcyte GmbH over a 10-year period starting upon commencement of commercial production. In the event of a termination under certain circumstances, Lonza shall be obligated to provide certain wind-down and transition services to Vaxcyte GmbH for up to 12 and 24 months, respectively.
Agreement termination penalty	$ 70,000,000
Repurposing fee	$ 27,000,000
Additional renewal period	5 years
Capital expenditure related to the facility build out and equipment		$ 51,800,000
Facility Build Out Expenidtures		34,700,000
Pre-commercial services fees		$ 3,000,000
RepurposingFees	$ 27,000,000

Balance Sheet Details - Schedul

Balance Sheet Details - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Prepaid expenses	$ 6,159	$ 5,312
Purchased equipment deposits	3,856	0
Interest receivable	3,598	2,848
Grant receivable	9	1,029
Other current assets	2,105	1,990
Total	$ 15,727	$ 11,179

Balance Sheet Details - Sched_2

Balance Sheet Details - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property Plant And Equipment [Line Items]
Total property and equipment	$ 88,898	$ 16,477
Less: accumulated depreciation and amortization	(9,272)	(6,117)
Property and equipment, net	79,626	10,360
Furniture and Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	1,608	1,608
Computers and Computer Software
Property Plant And Equipment [Line Items]
Total property and equipment	771	416
Lab Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	25,110	13,100
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	1,460	1,353
Manufacturing equipment and auxiliary
Property Plant And Equipment [Line Items]
Total property and equipment	8,134	0
Manufacturing facility and equipment construction-in-progress
Property Plant And Equipment [Line Items]
Total property and equipment	$ 51,815	$ 0

Balance Sheet Details - Sched_3

Balance Sheet Details - Schedule of Other Assets, Noncurrent (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Other Assets, Noncurrent [Abstract]
Manufacturing facility construction buildout	$ 34,688	$ 0
Long-term prepaid assets	2,768	4,361
Other long-term assets	106	194
Total	$ 37,562	$ 4,555

Balance Sheet Details - Additio

Balance Sheet Details - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 3.2	$ 2.6	$ 1.8

Balance Sheet Details - Sched_4

Balance Sheet Details - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accrued Liabilities, Current [Abstract]
Clinical studies	$ 2,156	$ 1,518
Other research and development	30,759	7,446
Acquired manufacturing rights	25,000	5,000
Other accrued expenses	1,900	1,411
Total	$ 59,815	$ 15,375

Leases - Additional Information

Leases - Additional Information (Details) $ in Thousands	1 Months Ended						12 Months Ended
	Sep. 30, 2023 USD ($)	Feb. 28, 2022	Jan. 31, 2021 RenewalOption	Nov. 30, 2020	Jul. 31, 2019	Jul. 31, 2016 RenewalOption	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Oct. 31, 2023 USD ($)
Lessee Lease Description [Line Items]
Operating lease right-of-use assets							$ 30,997	$ 21,288
Operating lease liabilities							29,224	17,941
Operating leases rent expense recognized							8,500	$ 7,900	$ 3,200
Assignment Agreement
Lessee Lease Description [Line Items]
Operating lease, agreement term	10 years
Operating lease, commencement date	Oct. 01, 2023
Assumed lease rental payment	$ 1,900
Operating lease rental adjustment	3%
Lease expiration date	Nov. 30, 2031
Operating lease right-of-use assets										$ 16,700
Operating lease liabilities										$ 16,800
Lonza Commercial Manufacturing And Supply Agreement [Member]
Lessee Lease Description [Line Items]
Operating lease liabilities							$ 0
Lessee, Operating Lease, Lease Not yet Commenced, Description							As of December 31, 2023, the lease had not commenced and, as such, no lease liability or ROU asset was recorded on the consolidated balance sheets and no operating lease expense was recorded on the consolidated statements of operations.
Operating leases rent expense recognized							$ 0
Headquarters Facility
Lessee Lease Description [Line Items]
Operating lease, agreement term						5 years
Operating lease, commencement date						Sep. 01, 2016
Lease termination date		Feb. 12, 2022
Lease expiration date						Aug. 31, 2021
Operating lease, renewal option | RenewalOption						2
Operating lease, renewal term						30 months
Operating lease, option to renewal, description							30-month renewal options
Operating lease, existence of option to renewal						true
Operating lease, description							In July 2016, we entered into a five-year lease agreement for our previous headquarters facility located in Foster City, California. The original term of the lease was from September 1, 2016 to August 31, 2021, with two 30-month renewal options.
Operating lease, extended term				6 months
Operating lease, extended maturity date				Mar. 01, 2022
Additional Facility
Lessee Lease Description [Line Items]
Operating lease, commencement date					Jul. 01, 2019
Lease expiration date					Oct. 31, 2021
Operating lease, option to renewal, description							no renewal options
Operating lease, existence of option to renewal					false
Operating lease, description							In July 2019, we leased another facility in Foster City, California. The original term of this lease was from July 1, 2019 to October 31, 2021, with no renewal options.
Operating lease, extended term				6 months
Operating lease, extended maturity date				Apr. 30, 2022
New Corporate Headquarters Facility
Lessee Lease Description [Line Items]
Operating lease, commencement date			Dec. 03, 2021
Lease expiration date			Dec. 31, 2025
Operating lease, renewal term			60 months
Operating lease, extended term			60 days
Number of renewal options | RenewalOption			2
Palo Alto
Lessee Lease Description [Line Items]
Operating lease, extended maturity date			Mar. 03, 2022
San Carlos
Lessee Lease Description [Line Items]
Operating lease right-of-use assets							$ 28,400
Operating lease liabilities							$ 12,900

Leases - Schedule of Informatio

Leases - Schedule of Information Related to ROU Assets and Lease Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Cash paid for operating lease liabilities	$ 7,390	$ 5,374
Operating lease right-of-use assets	30,997	21,288
Operating lease liabilities - current	7,113	5,910
Operating lease liabilities - long-term	22,111	12,031
Total lease liabilities	$ 29,224	$ 17,941
Weighted-average remaining lease term (in years)	5 years 8 months 15 days	2 years 9 months 10 days
Weighted-average discount rate	8.40%	7.60%

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
2024	$ 8,817
2025	9,836
2026	2,899
2027	2,986
2028	3,075
Thereafter	9,503
Total future undiscounted lease payments	37,115
Less: Imputed interest	(7,891)
Total lease liabilities	$ 29,224	$ 17,941

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions			12 Months Ended
	Nov. 21, 2023	Sep. 28, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Common Stock [Member]
Loss Contingencies [Line Items]
Number of common stock issued					399,680
Sutro Biopharma Inc [Member]
Loss Contingencies [Line Items]
Number of common stock issued				167,780
Upfront consideration				$ 22.5
Upfront consideration in cash				10
Upfront consideration in cash after agreement date				5
Option exercise price in cash		$ 25		75
Additional milestone payments in cash	$ 60			60
Accrued commitment			$ 25
Accrued payment	$ 50		$ 50	5
Fair value on date of settlement				8
Sutro Biopharma Inc [Member] | Common Stock [Member]
Loss Contingencies [Line Items]
Upfront consideration				$ 7.5

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Non-cancelable Purchase Commitments Related to Raw Materials (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2024	$ 181,812
2025	41,840
2026	1,296
2027	414
Total non-cancelable purchase commitments due to key manufacturing partners	$ 225,362

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($)				1 Months Ended		12 Months Ended
	Apr. 21, 2023	Oct. 28, 2022	Jan. 13, 2022	Feb. 27, 2023	Feb. 28, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jul. 31, 2021
Class Of Stock [Line Items]
Preferred stock, shares authorized						10,000,000	10,000,000
Preferred stock, par value per share						$ 0.001	$ 0.001
Common stock, shares authorized						500,000,000	500,000,000
Common stock, par value per share						$ 0.001	$ 0.001
Common stock, shares issued						95,364,831	79,470,670
Common stock, shares outstanding						95,364,831	79,470,670
Preferred stock, shares outstanding						0	0
Preferred stock, shares issued						0	0
Preferred stock ,dividends paid						$ 0	$ 0
Preferred stock ,dividends declared						0	0
Common stock, dividends, per share, declared						$ 0	$ 0
Common stock, voting rights						Each share of common stock is entitled to one vote
Proceeds from issuance of stock, net of commission and offering expenses						$ 90,741,000	$ 97,299,000	$ 13,896,000
Equity incentive plan, shares issued						36,710
Over Allotment Option
Class Of Stock [Line Items]
Shares issued	13,030,000	17,812,500	2,500,000
Common stock price per share	$ 41	$ 32	$ 20
Pre-funded warrants to purchase shares	1,000,000	3,750,000	2,500,000
Prefunded Warrants Price Per Share	$ 40.999	$ 31.999	$ 19.999
Underwriters' option to purchase additional shares	1,830,000	2,812,500			750,000
Net proceeds from follow on offering	$ 545,300,000	$ 651,600,000			$ 107,600,000
ATM Sales Agreement
Class Of Stock [Line Items]
Aggregate offering price				$ 150,000,000
ATM Sales Agreement | Jefferies LLC
Class Of Stock [Line Items]
Aggregate offering price				$ 137,800,000
Maximum commission percentage of gross proceeds from common stock sold									3%
Common stock shares sold				4,995,709		1,588,807
Average price				$ 27.57
Aggregate gross proceeds from issuance of common stock						$ 70,000,000
Proceeds from issuance of stock, net of commission and offering expenses						$ 68,600,000
Equity incentive plan, shares issued						44.06
ATM Sales Agreement | Maximum | Jefferies LLC
Class Of Stock [Line Items]
Aggregate offering price				$ 400,000,000					$ 150,000,000

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Common Stock Shares Reserved for Future Issuance (Details) - 2020 Plan and 2014 Plan - shares	Dec. 31, 2023	Dec. 31, 2022
Class Of Stock [Line Items]
Common stock reserved for future issuances	16,133,448	12,851,858
Employee Stock Option
Class Of Stock [Line Items]
Common stock reserved for future issuances	9,314,836	7,715,494
Restricted Stock Units (RSUs) [Member]
Class Of Stock [Line Items]
Common stock reserved for future issuances	753,462	456,766
Shares Available for Future Stock Option Grants
Class Of Stock [Line Items]
Common stock reserved for future issuances	6,065,150	4,679,598

Pre-Funded Warrants - Additiona

Pre-Funded Warrants - Additional Information (Details) - $ / shares	1 Months Ended
	Apr. 30, 2023	Oct. 31, 2022	Jan. 31, 2022	Dec. 31, 2023
Class of Stock [Line Items]
Warrant exercised	0.001	0.001	0.001	0
Increase or Decrease of Pre-funded Warrant Percentage Not Exceed	19.99%	19.99%	19.99%
Minimum
Class of Stock [Line Items]
Pre-funded warrants of common stock shares outstanding Immediately after effect to the exercise	4.99%	4.99%	4.99%
Combined voting power of securities outstanding immediately after effect to the exercise	4.99%	4.99%	4.99%
Maximum
Class of Stock [Line Items]
Pre-funded warrants of common stock shares outstanding Immediately after effect to the exercise	9.99%	9.99%	9.99%
Combined voting power of securities outstanding immediately after effect to the exercise	9.99%	9.99%	9.99%
Over Allotment Option
Class of Stock [Line Items]
Pre-funded warrants to purchase shares	1,000,000	3,750,000	2,500,000
Prefunded Warrants Price Per Share	$ 40.999	$ 31.999	$ 19.999
Pre-funded warrant recorded as a component of stockholders' equity within additional paid-in-capital	$ 0.001	$ 0.001	$ 0.001

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
	Jan. 01, 2023	Jun. 11, 2020	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage for stock options granted		25%
Vesting period for stock options granted		4 years
Early exercised stock options			0	3,705
Options granted			36,710
Exercise of stock options (in shares)			538,888	1,153,285	926,514
Weighted-average price per share			$ 10.5	$ 4.25	$ 3.25
Weighted-average grant date fair value of options granted			$ 28.74	$ 18.88	$ 14.65
Intrinsic value of the stock options exercised			$ 21.2	$ 34	$ 18.9
Unrecognized stock-based compensation expense			$ 127.5
Unrecognized share-based compensation expense, expected to be recognized			2 years 8 months 12 days
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage for stock options granted		25%
Vesting percentage for stock options granted, Six months thereafter		12.50%
Vesting period for stock options granted		4 years
Other Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting percentage for stock options granted, Six months thereafter		12.50%
Vesting period for stock options granted		3 years 6 months
Weighted-average grant date fair value of options granted			$ 45.57	$ 26.25
Unrecognized stock-based compensation cost			$ 25.9	$ 10.8
Unrecognized share-based compensation expense, expected to be recognized			2 years 8 months 12 days	3 years
2020 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price expire in years form the date of grant		5 years
Stock options granted term		10 years
Percentage of provisions subject to stockholders		10%
Shares reserved for issuance		10,150,000
Term of plan		10 years
Percentage of outstanding number of shares		5%
Aggregate number of shares available for issuance			6,065,150
Available for issuance of shares increased			4,768,241
2020 Equity Incentive Plan | Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares outstanding			7,840,335
2014 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares outstanding			2,227,963
2020 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance		650,000
Term of plan		10 years
Percentage of outstanding number of shares		1%
Available for issuance of shares increased	794,706
Employees purchase shares of common stock of lower of fair market value		85%
Offering period		2 years
Purchase period		6 months
Percentage of payroll deductions of eligible compensation		15%
Minimum | 2020 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Incentive stock option granted to employees owning percentage of shares of common stock		10%
Maximum | Other Liabilities
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Remaining liabilities related to early exercised shares			$ 0.1	$ 0.1
Maximum | 2020 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of fair value per share on the grant date		110%

Equity Incentive Plans - Summar

Equity Incentive Plans - Summary of Activity Under Stock Option Plans (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options, granted		36,710
Weighted-Average Exercise Price Per Share, Options exercised		$ 10.5	$ 4.25	$ 3.25
2020 Plan and 2014 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Available for Grant, Beginning Balance		4,679,598	6,104,756
Options Available for Grant, Additional shares authorized		3,973,533	2,651,598
Options Available for Grant, granted		(2,343,037)	(3,850,981)
Options Available for Grant, exercised	[1]	1,080	385
Options Available for Grant, forfeited		204,807	277,209
Options Available for Grant, Ending Balance		6,065,150	4,679,598	6,104,756
Number of Options, Beginning Balance		7,715,494	5,295,007
Number of Options, granted		2,343,037	3,850,981
Number of Options, exercised		(538,888)	(1,153,285)
Number of Options, forfeited		(204,807)	(277,209)
Number of Options, Ending Balance		9,314,836	7,715,494	5,295,007
Number of Options, Vested and expected to vest		9,314,836
Number of Options, Exercisable		4,646,989
Weighted-Average Exercise Price Per Share, Beginning Balance		$ 18.70	$ 9.30
Weighted-Average Exercise Price Per Share, Options granted		44.44	27.67
Weighted-Average Exercise Price Per Share, Options exercised		10.50	4.25
Weighted-Average Exercise Price Per Share, Options forfeited		32.58	23.54
Weighted-Average Exercise Price Per Share, Ending Balance		25.35	$ 18.70	$ 9.30
Weighted-Average Exercise Price Per Share, Vested and expected to vest		25.35
Weighted-Average Exercise Price Per Share, Exercisable		$ 16.4
Weighted-Average Remaining Contractual Term (Years)		7 years 9 months	8 years 2 months 12 days
Weighted-Average Remaining Contractual Term (Years), Vested and expected to vest		7 years 9 months
Weighted-Average Remaining Contractual Term (Years), Exercisable		6 years 9 months 18 days
Aggregate Intrinsic Value		$ 348,868	$ 225,667
Aggregate Intrinsic Value, Vested and expected to vest		348,868
Aggregate Intrinsic Value, Exercisable		$ 215,608
2020 Plan and 2014 Plan | Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options Available for Grant, granted		(574,123)	(581,047)
Options Available for Grant, forfeited		44,537	45,052
Restricted Stock Units withheld		78,755	32,626
[1] .

Equity Incentive Plans - Nonves

Equity Incentive Plans - Nonvested Restricted Stock Shares Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Begining balance	456,766	0
Granted	574,123	581,047
Vested and released	(232,890)	(79,229)
Cancelled	(44,537)	(45,052)
Ending balance	753,462	456,766
Weighted average grant date fair value, Beginning balance	$ 26,700	$ 0
Weighted average grant date fair value, granted	45,570	26,250
Weighted average grant date fair value, Vested and released	30,970	24,790
Weighted average grant date fair value, Cancelled	40,780	24,320
Weighted average grant date fair value, Ending balance	$ 38,930	$ 26,700

Equity Incentive Plans - Summ_2

Equity Incentive Plans - Summary of Activity under Employee Stock Purchase Plan (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Begining balance	456,766	0
Ending balance	753,462	456,766
2020 Employee Stock Purchase Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Begining balance	1,539,314	1,070,704
Additional shares authorized	794,706	530,319
Shares purchased	(76,275)	(61,709)
Ending balance	2,257,745	1,539,314

Equity Incentive Plans - Summ_3

Equity Incentive Plans - Summary of Estimated Fair Value of Employee Stock Options (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value Assumptions
Expected volatility, Minimum	71.30%	78.10%	81%
Expected volatility, Maximum	74%	85.10%	84.10%
Expected dividend yield	0%	0%	0%
Risk-free interest rate, Minimum	3.50%	1.60%	0.50%
Risk-free interest rate, Maximum	4.60%	4.40%	1.30%
Minimum
Fair Value Assumptions
Expected term (in years)	5 years 3 months 18 days	5 years 3 months 18 days	5 years 3 months 18 days
Maximum
Fair Value Assumptions
Expected term (in years)	5 years 4 months 24 days	5 years 6 months	5 years 6 months

Equity Incentive Plans - Summ_4

Equity Incentive Plans - Summary of Estimated Fair Value of Shares Under Employee Stock Purchase Plan (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value Assumptions
Expected volatility, Minimum	71.30%	78.10%	81%
Expected volatility, Maximum	74%	85.10%	84.10%
Expected dividend yield	0%	0%	0%
Risk-free interest rate, Minimum	3.50%	1.60%	0.50%
Risk-free interest rate, Maximum	4.60%	4.40%	1.30%
Minimum
Fair Value Assumptions
Expected term (in years)	5 years 3 months 18 days	5 years 3 months 18 days	5 years 3 months 18 days
Maximum
Fair Value Assumptions
Expected term (in years)	5 years 4 months 24 days	5 years 6 months	5 years 6 months
2020 Employee Stock Purchase Plan
Fair Value Assumptions
Expected volatility, Minimum	38.10%	78.80%	79.60%
Expected volatility, Maximum	99.70%	99.70%	126.30%
Expected dividend yield	0%	0%	0%
Risk-free interest rate, Minimum	4.20%	0.10%	0%
Risk-free interest rate, Maximum	5.40%	4.70%	0.50%
2020 Employee Stock Purchase Plan | Minimum
Fair Value Assumptions
Expected term (in years)	6 months	6 months	6 months
2020 Employee Stock Purchase Plan | Maximum
Fair Value Assumptions
Expected term (in years)	2 years	2 years	2 years

Equity Incentive Plans - Summ_5

Equity Incentive Plans - Summary of Stock-based Compensation Expense (Details) - 2014 Plan, 2020 Plan and 2020 ESPP - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 48,760	$ 23,650	$ 10,729
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	23,275	9,899	3,954
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 25,485	$ 13,751	$ 6,775

Retirement Plan - Additional In

Retirement Plan - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits [Abstract]
Company contributions	$ 1.4	$ 0.8	$ 0

Funding Arrangement - Additiona

Funding Arrangement - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Jun. 30, 2023	Apr. 30, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jul. 31, 2019
Funding Arrangement [Line Items]
Grant income			$ 4,765	$ 1,931	$ 1,585
Cost Reimbursement Sub-Award Agreement
Funding Arrangement [Line Items]
Grant income			4,800	1,900	$ 1,600
CARB-X Agreement
Funding Arrangement [Line Items]
Grant receivable on unreimbursed, eligible costs incurred			$ 0	$ 1,000
CARB-X Agreement | Maximum
Funding Arrangement [Line Items]
Initial funding committed by award						$ 14,600
CARB-X Agreement | Minimum
Funding Arrangement [Line Items]
Potential funding committed by award						$ 11,700
National Institutes of Health
Funding Arrangement [Line Items]
Potential funding amount of award to develop vaccine to prevent shingella infections	$ 4,600	$ 500
National Institutes of Health | Maximum
Funding Arrangement [Line Items]
Potential funding period of award to develop vaccine to prevent shingella infections	5 years	5 years

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Earnings Per Share [Abstract]
Net loss (in thousands)		$ (402,266)	$ (223,485)	$ (100,077)
Weighted Average Number of Shares Outstanding, Basic	[1]	97,157,690	64,877,988	51,922,108
Weighted Average Number of Shares Outstanding, Diluted	[1]	97,157,690	64,877,988	51,922,108
Earnings Per Share, Basic		$ (4.14)	$ (3.44)	$ (1.93)
Earnings Per Share, Diluted		$ (4.14)	$ (3.44)	$ (1.93)
[1] Includes shares of common stock into which pre-funded warrants may be exercised. See Note 9, “Pre-Funded Warrants.”

Net Loss Per Share - Schedule_2

Net Loss Per Share - Schedule of Potentially Dilutive Securities Excluded From Computation of Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	10,208,636	8,322,210	5,423,793
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	753,462	456,766	0
Employee Stock Purchase Plan [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	103,628	113,240	66,404
Employee Stock Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	9,351,546	7,752,204	5,357,389

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory Rate	21%	21%	21%
Stock-based Compensation	0.50%	1.50%	2.20%
Credits	1.40%	0.80%	1.10%
Change in valuation allowance	(21.80%)	(21.30%)	(23.00%)
Section 162(m) Limitation	(1.10%)	(1.80%)	(1.10%)
Other	0%	(0.20%)	(0.20%)
Total	0%	0%	0%

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating losses	$ 135,298	$ 111,555
Fixed assets	660	1,062
Accrued and others	11,279	1,103
R&D Credits	12,870	5,436
Capitalized R&D expenditures	79,485	32,873
Accrued manufacturing expenses	10,819	2,063
Lease Liability	8,739	5,358
Intangible assets	29,302	6,867
Stock compensation	8,981	4,474
Total	297,434	170,791
Deferred tax liabilities:
ROU asset	(9,269)	(6,357)
Total deferred tax liabilities	(9,269)	(6,357)
Net deferred tax asset	288,165	164,433
Valuation allowance	(288,165)	(164,433)
Net deferred taxes	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Line Items]
Uncertain tax benefits	$ 4,447,000	$ 1,754,000	$ 924,000	$ 393,000
Interest or penalties recognized for the period	0	$ 0
Federal
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	351,900,000
Research credit carryforwards	$ 12,800,000
Tax credit carry forwards expiration year	2039
Research and experimental expenses amortized period	5 years
Federal | Research | Maximum
Income Tax Disclosure [Line Items]
Research credit carryforward	$ 0
State
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 693,600,000
Operating loss carry forwards expiration year	2034
Foreign
Income Tax Disclosure [Line Items]
Research and experimental expenses amortized period	15 years
California
Income Tax Disclosure [Line Items]
Research credit carryforwards	$ 4,600,000

Income Taxes - Reconciliation_2

Income Taxes - Reconciliation of Unrecognized Tax Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at the beginning of the year	$ 1,754	$ 924	$ 393
Additions based on tax positions related to current year	2,208	876	461
Additions based on tax positions related to prior years	485	(46)	70
Balance at end of year	$ 4,447	$ 1,754	$ 924

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	May 29, 2018	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Apr. 30, 2023	Oct. 31, 2022	Jan. 31, 2022	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Common stock, shares owned		95,364,831	79,470,670
Warrant exercised		0			0.001	0.001	0.001
Sutro Biopharma, Inc
Related Party Transaction [Line Items]
Common stock, shares owned				1,600,000				1,600,000
Sutro Biopharma, Inc | License Agreement
Related Party Transaction [Line Items]
Percentage of royalty payment on annual net sales of vaccine products for human health		4%
Percentage of royalty payment on net sales of vaccine compositions for animal health		2%
Sutro Biopharma, Inc | Supply Agreement
Related Party Transaction [Line Items]
Expenses related to Supply Agreement		$ 0	$ 0	$ 2.4
Sutro Biopharma, Inc | Series C Redeemable Convertible Stock
Related Party Transaction [Line Items]
Warrant to purchase shares of stock									59,276
Warrant purchase price per share									$ 11.5215
Sutro Biopharma, Inc | Series C Redeemable Convertible Stock | License Amendment A2
Related Party Transaction [Line Items]
Warrant to purchase shares of stock	59,276
Warrant purchase price per share	$ 11.5215
Warrant exercisable and vests immediately and expires date	May 29, 2018
Sutro Biopharma, Inc | Common Stock
Related Party Transaction [Line Items]
Warrant to purchase shares of stock									31,857
Warrant purchase price per share									$ 0.79289
Sutro Biopharma, Inc | Common Stock Warrant
Related Party Transaction [Line Items]
Warrant exercised									30,278
Sutro Biopharma, Inc | Preferred Stock Warrant
Related Party Transaction [Line Items]
Warrant exercised									16,591

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - Underwritten Public Offering - USD ($) $ / shares in Units, $ in Millions		1 Months Ended
	Feb. 02, 2024	Apr. 30, 2023	Oct. 31, 2022	Jan. 31, 2022
Subsequent Event [Line Items]
Pre-funded warrants to purchase shares		1,000,000	3,750,000	2,500,000
Pre-funded warrants price per share		$ 40.999	$ 31.999	$ 19.999
Subsequent Event
Subsequent Event [Line Items]
Shares issued	12,695,312
Underwriters' option to purchase additional shares	1,757,812
Common stock price per share	$ 64
Pre-funded warrants to purchase shares	781,250
Pre-funded warrants price per share	$ 63.999
Net proceeds from follow on offering	$ 816.5