Vaxcyte (PCVX) 10-Q 7 Nov 22 2022 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2022	Nov. 03, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Entity Registrant Name	VAXCYTE, INC.
Entity Central Index Key	0001649094
Current Fiscal Year End Date	--12-31
Entity Emerging Growth 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 Incorporation, State or Country Code	DE
Entity Address, Postal Zip Code	94070
City Area Code	650
Local Phone Number	837-0111
Document Quarterly Report	true
Document Transition Report	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		78,980,196
Entity Filer Category	Large Accelerated Filer
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Title of 12(b) Security	Common Stock, $0.001 par value per share
Trading Symbol	PCVX
Security Exchange Name	NASDAQ

Condensed Balance Sheets (Unaud

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 278,401	$ 68,985
Short-term investments	83,825	176,985
Prepaid expenses and other current assets	7,533	10,378
Total current assets	369,759	256,348
Property and equipment, net	9,947	7,954
Operating lease right-of-use assets	22,887	27,958
Long-term investments	3,977	27,117
Restricted cash	871	871
Other assets	4,624	4,089
Total noncurrent assets	42,306	67,989
Total assets	412,065	324,337
Current liabilities:
Accounts payable	5,485	6,758
Accrued compensation	3,451	3,455
Accrued manufacturing expenses	10,269	4,440
Accrued expenses	13,678	8,787
Operating lease liabilities — current	6,426	5,276
Total current liabilities	39,309	28,716
Operating lease liabilities — long-term	13,356	11,507
Other liabilities	89	96
Total liabilities	52,754	40,319
Commitments and contingencies (Note 6)
Stockholders' Equity
Preferred stock, $0.001 par value - 10,000,000 shares authorized at September 30, 2022 and December 31, 2021; no shares issued and outstanding at September 30, 2022 and December 31, 2021	0	0
Common stock, $0.001 par value - 500,000,000 shares authorized at September 30, 2022 and December 31, 2021; 60,572,692 and 53,031,978 shares issued and outstanding at September 30, 2022 and December 31, 2021, respectively	64	56
Additional paid-in capital	803,980	582,844
Accumulated other comprehensive loss	(657)	(241)
Accumulated deficit	(444,076)	(298,641)
Total stockholders' equity	359,311	284,018
Total liabilities and stockholders' equity	$ 412,065	$ 324,337

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) (Unaudited) - $ / shares	Sep. 30, 2022	Dec. 31, 2021
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	60,572,692	53,031,978
Common stock, shares outstanding	60,572,692	53,031,978

Condensed Statements of Operati

Condensed Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Operating expenses:
Research and development (including related party expenses of $0) and $0 for the three months ended September 30, 2022 and 2021,respectively, and $0 and $2,359 for the nine months ended September 30, 2022 and 2021, respectively)	$ 47,679	$ 20,428	$ 117,825	$ 55,337
General and administrative	10,898	6,523	27,858	18,487
Total operating expenses	58,577	26,951	145,683	73,824
Loss from operations	(58,577)	(26,951)	(145,683)	(73,824)
Other income (expense), net:
Interest Expense	0	0	(2)	(7)
Interest income	1,190	90	1,723	245
Grant income	157	299	1,006	677
Realized gain on marketable securities	0	1	0	2
Foreign currency transaction gains	(687)	(54)	(2,479)	1,393
Total other income (expense), net	660	336	248	2,310
Net loss	$ (57,917)	$ (26,615)	$ (145,435)	$ (71,514)
Net loss per share, basic	$ (0.93)	$ (0.51)	$ (2.42)	$ (1.39)
Net loss per share, diluted	$ (0.93)	$ (0.51)	$ (2.42)	$ (1.39)
Weighted-average shares outstanding, basic	61,989,347	52,187,303	60,166,583	51,627,249
Weighted-average shares outstanding, diluted	61,989,347	52,187,303	60,166,583	51,627,249

Condensed Statements of Opera_2

Condensed Statements of Operations (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Income Statement [Abstract]
Research and development expense to related party	$ 0	$ 0	$ 0	$ 2,359

Condensed Statements of Compreh

Condensed Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net Loss	$ (57,917)	$ (26,615)	$ (145,435)	$ (71,514)
Other comprehensive loss:
Unrealized gains (losses) on investments	247	(4)	(416)	(12)
Comprehensive loss	$ (57,670)	$ (26,619)	$ (145,851)	$ (71,526)

Condensed Statements of Redeema

Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity - USD ($)	Total	Lonza Ltd.	Common Stock	Common Stock Lonza Ltd.	Additional Paid-in Capital	Additional Paid-in Capital Lonza Ltd.	Accumulated Deficit	Accumulated Other Comprehensive Loss	Follow on public offering	Follow on public offering Common Stock	Follow on public offering Additional Paid-in Capital	At the market offering	At the market offering Common Stock	At the market offering Additional Paid-in Capital
Beginning balance at Dec. 31, 2020	$ 345,843,000		$ 54,000		$ 544,353,000		$ (198,564,000)
Beginning balance, shares at Dec. 31, 2020			51,071,593
Exercise of stock options	487,000		$ 267,208,000		487,000
Vesting of early exercised stock options	9,000				9,000
Stock-based compensation expense	1,865,000				1,865,000
Unrealized gains (losses) on investments	(47,000)							$ (47,000)
Net Loss	(21,220,000)						(21,220,000)
Ending balance at Mar. 31, 2021	326,937,000		$ 54,000		546,714,000		(219,784,000)	(47,000)
Ending balance, shares at Mar. 31, 2021			51,338,801
Beginning balance at Dec. 31, 2020	345,843,000		$ 54,000		544,353,000		(198,564,000)
Beginning balance, shares at Dec. 31, 2020			51,071,593
Release of restricted stock units, value	0
Net Loss	(71,514,000)
Ending balance at Sep. 30, 2021	305,956,000		$ 56,000		575,990,000		(270,078,000)	(12,000)
Ending balance, shares at Sep. 30, 2021			52,587,855
Beginning balance at Mar. 31, 2021	326,937,000		$ 54,000		546,714,000		(219,784,000)	(47,000)
Beginning balance, shares at Mar. 31, 2021			51,338,801
Exercise of stock options	466,000		$ 190,003		466,000
Vesting of early exercised stock options	2,000				2,000
Issuance of common stock under employee stock purchase plan	490,000				490,000
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)			35,286
Issuance of common stock, value		$ 10,001,000		$ 1,000		$ 10,000,000
Issuance of common stock, shares		399,680
Stock-based compensation expense	2,769,000				2,769,000
Unrealized gains (losses) on investments	39,000							39,000
Net Loss	(23,679,000)						(23,679,000)
Ending balance at Jun. 30, 2021	317,025,000		$ 55,000		560,441,000		(243,463,000)	(8,000)
Ending balance, shares at Jun. 30, 2021			51,963,770
Exercise of stock options	491,000				491,000
Exercise of stock options (in shares)			125,583
Vesting of early exercised stock options	2,000				2,000
Issuance of common stock, value												$ 12,120,000	$ 1,000	$ 12,119,000
Issuance of common stock, shares													498,502
Stock-based compensation expense	2,937,000				2,937,000
Unrealized gains (losses) on investments	(4,000)							(4,000)
Net Loss	(26,615,000)						(26,615,000)
Ending balance at Sep. 30, 2021	305,956,000		$ 56,000		575,990,000		(270,078,000)	(12,000)
Ending balance, shares at Sep. 30, 2021			52,587,855
Beginning balance at Dec. 31, 2021	284,018,000		$ 56,000		582,844,000		(298,641,000)	(241,000)
Beginning balance, shares at Dec. 31, 2021			53,031,978
Exercise of stock options	282,000				282,000
Exercise of stock options (in shares)			91,044
Vesting of early exercised stock options	2,000				2,000
Issuance of common stock, value									$ 107,622,000	$ 3,000	$ 107,619,000	3,098,000		3,098,000
Issuance of common stock, shares										3,250,000			126,522
Stock-based compensation expense	4,099,000				4,099,000
Unrealized gains (losses) on investments	(592,000)							(592,000)
Net Loss	(38,986,000)						(38,986,000)
Ending balance at Mar. 31, 2022	359,543,000		$ 59,000		697,944,000		(337,627,000)	(833,000)
Ending balance, shares at Mar. 31, 2022			56,499,544
Beginning balance at Dec. 31, 2021	284,018,000		$ 56,000		582,844,000		(298,641,000)	(241,000)
Beginning balance, shares at Dec. 31, 2021			53,031,978
Release of restricted stock units, value	861,000
Net Loss	(145,435,000)
Ending balance at Sep. 30, 2022	359,311,000		$ 64,000		803,980,000		(444,076,000)	(657,000)
Ending balance, shares at Sep. 30, 2022			60,572,692
Beginning balance at Mar. 31, 2022	359,543,000		$ 59,000		697,944,000		(337,627,000)	(833,000)
Beginning balance, shares at Mar. 31, 2022			56,499,544
Exercise of stock options	324,000		$ 1,000		323,000
Exercise of stock options (in shares)			77,065
Vesting of early exercised stock options	2,000				2,000
Issuance of common stock under employee stock purchase plan	550,000				550,000
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)			36,879
Issuance of common stock, value									$ 2,000		$ 2,000	48,788,000	$ 2,000	48,786,000
Issuance of common stock, shares													2,010,806
Stock-based compensation expense	5,894,000				5,894,000
Unrealized gains (losses) on investments	(71,000)							(71,000)
Net Loss	(48,532,000)						(48,532,000)
Ending balance at Jun. 30, 2022	366,500,000		$ 62,000		753,501,000		(386,159,000)	(904,000)
Ending balance, shares at Jun. 30, 2022			58,624,294
Exercise of stock options	1,757,000		$ 222,358,000		1,757,000
Vesting of early exercised stock options	2,000				2,000
Issuance of common stock, value												$ 42,935,000	$ 2,000	$ 42,933,000
Issuance of common stock, shares													1,679,437
Release of restricted stock units, value	(861,000)				(861,000)
Release of restricted stock units, shares			46,603
Stock-based compensation expense	6,648,000				6,648,000
Unrealized gains (losses) on investments	247,000							247,000
Net Loss	(57,917,000)						(57,917,000)
Ending balance at Sep. 30, 2022	$ 359,311,000		$ 64,000		$ 803,980,000		$ (444,076,000)	$ (657,000)
Ending balance, shares at Sep. 30, 2022			60,572,692

Condensed Statements of Redee_2

Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021
Issuance costs			$ 7,376
Common Stock | At the market offering
Issuance costs	$ 1,261	$ 1,509	$ 114	$ 41

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flows from operating activities:
Net loss	$ (145,435)	$ (71,514)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,875	1,341
Stock-based compensation expense	16,641	7,571
Amortization of operating right-of-use assets	5,021	910
Net amortization of premiums on investments	228	910
Loss on disposal of fixed assets	44	32
Asset impairment charges	213	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	2,852	(16,306)
Other assets	(534)	(3,030)
Operating lease liabilities	2,991	(75)
Accounts payable	(575)	5,601
Accrued compensation	(4)	1,791
Accrued manufacturing expenses	5,830	(5,979)
Accrued expenses	5,477	8,448
Net cash used in operating activities	(105,376)	(70,300)
Cash flows from investing activities:
Purchases of property and equipment	(4,701)	(5,173)
Proceeds from sale of property and equipment	7	0
Purchases of investments	(31,460)	(295,279)
Maturities of investments	136,191	58,000
Sale of investments	10,500	30,062
Net cash provided by (used in) investing activities	110,537	(212,390)
Cash flows from financing activities:
Proceeds from exercise of common stock options	2,363	1,444
Proceeds from issuance of common stock related to at-the-market offering, net of commissions and offering expenses	95,238	7,108
Proceeds from issuance of common stock from follow-on offering, net of issuance costs	107,624	0
Release of restricted stock units	(861)	0
Proceeds from issuance of common stock under the Employee Stock Purchase Plan	550	490
Net cash provided by financing activities	204,914	9,042
Effect of exchange rate changes on cash and cash equivalents	(659)	363
Net increase (decrease) in cash, cash equivalents and restricted cash	209,416	(273,285)
Cash, cash equivalents and restricted cash, beginning of period	69,856	386,200
Cash, cash equivalents and restricted cash, end of period	279,272	112,915
Cash paid for interest	2	7
Supplemental disclosures of non-cash investing and financing activities:
Purchases of property and equipment recorded in accounts payable and accrued expenses	141	271
Stock issued for payment of accounts payable	0	10,000
Proceeds from issuance of common stock through ATM facility not yet received	0	5,011
Deferred offering costs included in accounts payable and accrued expenses	$ 0	$ 154

Company Organization and Nature

Company Organization and Nature of Business	9 Months Ended
	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Company Organization and Nature of Business	1. Company Organization and Nature of Business Vaxcyte, Inc. (“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. 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. 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 the 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	9 Months Ended
	Sep. 30, 2022
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 These condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or U.S. GAAP, and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and footnote disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted in accordance with such rules and regulations. Unaudited Interim Condensed Financial Statements The condensed balance sheet as of September 30, 2022, the condensed statements of operations, comprehensive loss and stockholders’ equity for the three and nine months ended September 30, 2022 and 2021 and the condensed statements of cash flows for the nine months ended September 30, 2022 and 2021 are unaudited. The unaudited interim condensed financial statements have been prepared on the same basis as the audited annual financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair statement of our financial information. The financial data disclosed in the footnotes to the condensed financial statements related to the three and nine months ended September 30, 2022 and 2021 are also unaudited. The results of operations for the three and nine months ended September 30, 2022 are not necessarily indicative of the results to be expected for the year ending December 31, 2022 or for any other future annual or interim period. These interim condensed financial statements should be read in conjunction with our audited financial statements and related notes thereto for the year ended December 31, 2021 included in our Annual Report on Form 10-K filed with the SEC on February 28, 2022. Use of Estimates The preparation of 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 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 determination of our 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. 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 and cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts and commercial paper and are stated at their fair values. Restricted cash consists of a standby letter of credit, which was issued in the first quarter of 2021, that serves as collateral for the lease agreement for our new corporate headquarters. Cash, cash equivalents and restricted cash as reported within the condensed balance sheets that total to the same amounts shown in the condensed statement of cash flows are as follows: September 30, December 31, 2022 2021 (in thousands) Cash and cash equivalents $ 278,401 $ 68,985 Restricted cash 871 871 Cash, cash equivalents and restricted cash $ 279,272 $ 69,856 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 condensed balance sheets at fair value. Unrealized gains and losses on these securities are included as a separate component of accumulated other comprehensive 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 condensed 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 income, and are recognized in our condensed consolidated statements of operations only if we sell or intend to sell the security before recovery of its cost basis. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted average of shares of common stock outstanding, including pre-funded warrants issued, during the period, without consideration for common stock equivalents. 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. Diluted net loss per share is the same as basic net loss per share since the effects of potentially dilutive securities are antidilutive given the net loss for each period presented. Deferred Offering Costs Deferred offering costs consist of fees and expenses incurred in connection with the sale of our common stock in equity transactions, including legal, accounting, printing and other issuance-related costs. Prior to the completion of such equity transactions, these deferred offering costs were included in Other assets on the condensed balance sheet. In connection with and as of the closing of such equity transactions, these costs were reclassified to Additional paid-in capital, representing a reduction to the gross proceeds. As of September 30, 2022 and December 31, 2021 , we recorded deferred offering costs of $ 0.2 million and $ 0.5 million, respectively, in Other assets on the condensed balance sheets. Leases Under Financial Accounting Standards Board ("FASB") Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842) and its associated amendments (“ASC 842”), 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 September 30, 2022, our lease population consisted of real estate operating leases. As of September 30, 2022 , we did no t have 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 condensed balance sheet. 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 us. 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 and lease 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 condensed balance sheets. 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 and 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 condensed balance sheets. 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 our suppliers. We source our critical raw materials from a sole source supplier, Sutro Biopharma, Inc. (“Sutro Biopharma”). We also use one contract manufacturing organization (“CMO”), Lonza Ltd. (“Lonza”), to handle most of our manufacturing activities. If we were to experience disruptions in raw materials supplied by Sutro Biopharma, 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 clinical or preclinical stages of 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 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; our ability to obtain additional capital to finance our operations; our ability to obtain, maintain and protect our intellectual property 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 Quarterly Report on Form 10-Q. Recently Adopted Accounting Pronouncements In November 2021, the FASB issued ASU 2021-10, Government Assistance (Topic 832): Disclosure by Business Entities about Government Assistance , which requires disclosures about transactions with a government entity that are accounted for by applying a grant or contribution accounting model by analogy to other accounting guidance, such as a grant model within International Accounting Standard 20, Accounting for Government Grants and Disclosure of Government Assistance (Subtopic 958-605), Not-For-Profit Entities - Revenue Recognition . The required disclosures include (i) the nature of the transaction and the related accounting policy used to account for the transaction, (ii) the financial statement line items that are affected by the transactions and (iii) the significant terms and conditions of the transactions, including commitments and contingencies. This standard is effective for annual periods beginning after December 15, 2021, with early adoption and retrospective or prospective application permitted. This standard is effective for us on January 1, 2022 and only impacts annual financial statement footnote disclosures. In Note 10, "Funding Arrangement," we included disclosures on our cost-reimbursement research award from Combating Antibiotic Resistant Bacteria Biopharmaceutical Accelerator ("CARB-X"). We have adopted this standard as required by the effective date. The adoption of this standard did not have a material impact on our financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments and has subsequently issued related amendments, collectively referred to as “Topic 326.” Topic 326 requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions and reasonable and supportable forecasts that affect collectability. Topic 326 also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. We have adopted this standard as required by the effective date on January 1, 2022. The adoption of this standard did not have a material impact on our financial statements.

Fair Value Measurements and Fai

Fair Value Measurements and Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2022
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 condensed 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 based on our own data or other assumptions 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 as of September 30, 2022 or December 31, 2021. There were no transfers within the hierarchies during the three and nine months ended September 3 0 , 2 0 22 or the year ended December 31, 2 0 21. The Company evaluated its securities for other-than-temporary impairment and considered the decline in market value to be primarily attributable to current economic and market conditions and would not be required to sell the securities before recovery of the amortized cost basis. Based on this analysis, these marketable securities were not considered to be other-than temporarily impaired as of September 30, 2022 and December 31, 2021. The following tables set forth our financial instruments measured at fair value on a recurring basis by level within the fair value hierarchy at September 30, 2022 and December 31, 2021: September 30, 2022 Fair Value Amortized Gross Gross Fair Assets (in thousands) Cash and cash equivalents: Cash Level 1 $ 168,010 $ — $ — $ 168,010 Money market funds Level 1 29,927 — — 29,927 U.S. Treasury securities Level 1 — — — — Commercial paper Level 2 36,561 — ( 6 ) 36,555 U.S. government agency securities Level 2 43,903 6 — 43,909 Total cash and cash equivalents 278,401 6 ( 6 ) 278,401 Investments: U.S. Treasury securities Level 1 27,890 — ( 161 ) 27,729 Commercial paper Level 2 23,720 — ( 16 ) 23,704 Corporate debt Level 2 21,096 — ( 275 ) 20,821 Asset-backed securities Level 2 3,252 — ( 4 ) 3,248 U.S. government agency securities Level 2 12,501 — ( 201 ) 12,300 Total investments 88,459 — ( 657 ) 87,802 Total assets measured at fair value $ 366,860 $ 6 $ ( 663 ) $ 366,203 December 31, 2021 Fair Value Amortized Gross Gross Fair Assets (in thousands) Cash and cash equivalents: Cash Level 1 $ 27,834 $ — $ — $ 27,834 Money market funds Level 1 17,555 — — 17,555 Commercial paper Level 2 23,597 — ( 1 ) 23,596 Total cash and cash equivalents 68,986 — ( 1 ) 68,985 Investments: U.S. Treasury securities Level 1 45,290 — ( 73 ) 45,217 Commercial paper Level 2 61,941 — ( 22 ) 61,919 Corporate debt Level 2 58,498 — ( 74 ) 58,424 Asset-backed securities Level 2 13,899 — ( 25 ) 13,874 U.S. government agency securities Level 2 24,714 — ( 46 ) 24,668 Total investments 204,342 — ( 240 ) 204,102 Total assets measured at fair value $ 273,328 $ — $ ( 241 ) $ 273,087 The following table presents the contractual maturities of our investments as of September 30, 2022 (in thousands): September 30, 2022 Fair Value Due in less than one year $ 83,825 Due in one to five years 3,977 Total $ 87,802

Balance Sheet Details

Balance Sheet Details	9 Months Ended
	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Details	4. Balance Sheet Details Property and Equipment, Net Property and equipment, net as of September 30, 2022 and December 31, 2021 consisted of the following: September 30, December 31, 2022 2021 (in thousands) Furniture and equipment $ 1,608 $ 1,619 Computers and computer software 416 430 Lab equipment 11,986 9,453 Leasehold improvements 1,352 — Total property and equipment 15,362 11,502 Less: accumulated depreciation and amortization ( 5,415 ) ( 3,548 ) Property and equipment, net $ 9,947 $ 7,954 Depreciation and amortization expense for the three months ended September 30, 2022 and 2021 was $ 0.7 million and $ 0.5 million, respectively. Depreciation and amortization expense for the nine months ended September 30, 2022 and 2021 was $ 1.9 million and $ 1.3 million, respectively. Accrued Expenses Accrued expenses as of September 30, 2022 and December 31, 2021 consisted of the following : September 30, December 31, 2022 2021 (in thousands) Clinical studies $ 3,379 $ 453 Other research and development 8,718 4,676 Other accrued expenses 1,581 3,658 Total $ 13,678 $ 8,787

Leases

Leases	9 Months Ended
	Sep. 30, 2022
Leases [Abstract]
Leases	5. Leases Operating Lease Obligations In July 2016, we entered into a five-year lease agreement for our prior 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 as a result of growth in personnel and lab space requirements. 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 both 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. In January 2021, we entered into a lease agreement for our new corporate headquarters facility in San Carlos, California and a license agreement for temporary lab and office space in Palo Alto, California. The lease term for our new corporate headquarters facility expires December 31, 2025 . We have two 60 -month renewal options. 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 new corporate headquarters. We extended the license agreement for the Palo Alto office by 60 days to March 3, 2022 to accommodate our relocation plan. These two leases are accounted for as a combined lease because the contracts were negotiated as a package with the same commercial objective. Information related to our ROU assets and related lease liabilities was as follows (dollar amounts in thousands): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, 2022 2021 2022 2021 Cash paid for operating lease liabilities $ 1,631 $ 350 $ 3,743 $ 920 Operating lease right-of-use assets 22,887 307 Current operating lease liabilities $ 6,426 $ 613 Non-current operating lease liabilities 13,356 553 Total lease liabilities $ 19,782 $ 1,166 Weighted-average remaining lease term (in years) 3.04 0.32 Weighted-average discount rate 7.6 % 7.2 % Maturities of lease liabilities as of September 30, 2022 were as follows: Years ending December 31, (in thousands) Remainder of 2022 $ 1,631 2023 6,684 2024 6,850 2025 7,022 Thereafter — Total future undiscounted lease payments 22,187 Less: Imputed interest ( 2,405 ) Total lease liabilities $ 19,782 Future minimum payments required under operating leases as of December 31, 2021 were as follows: Years ending December 31, (in thousands) 2022 (1) $ ( 105 ) 2023 6,639 2024 6,805 2025 6,976 Thereafter — Total future undiscounted lease payments 20,315 Less: Imputed interest ( 3,532 ) Total lease liabilities $ 16,783 (1) Maturities for 2022 are net of lease incentives of $ 0.9 million allocated to the Palo Alto office. Rent expense recognized under the leases was $ 1.9 million and $ 1.0 million for the three months ended September 30, 2022 and 2021, respectively, and $ 6.0 million and $ 1.9 million for the nine months ended September 30, 2022 and 2021 , respectively.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. 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 September 30, 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 director and officer 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 Agreement On October 21, 2016, we entered into a development and manufacturing services agreement, as amended, with Lonza (the “Lonza DMSA”), pursuant to which Lonza is obligated to perform services including manufacturing process development and the manufacture of components for VAX-24, including the polysaccharide antigens, our proprietary eCRM protein carrier and conjugated drug substances. In September 2017, we and Lonza agreed to defer the completion payments for any stage that commenced after December 31, 2019 or had not been completed by December 31, 2019 until the earlier of the completion of all Investigational New Drug (“IND”)-enabling activities or December 31, 2020. In March 2020, Lonza agreed to defer the completion payments until the earlier of the completion of all IND-enabling activities or April 30, 2021. In April 2021, Lonza further agreed to defer 50 % of the completion payments until the earlier of the completion of all IND-enabling activities or December 31, 2021. In June 2018, we and Lonza entered into a letter agreement pursuant to which we agreed to certain terms for potential future payments in shares of our common stock as partial satisfaction of future obligations to Lonza. This agreement states that the initial pre-IND cash payments would be subject to a specified dollar cap (the “Initial Cash Cap”). After the Initial Cash Cap has been reached, we would have the option to make any further pre-IND payments owed to Lonza in cash, in shares of our common stock at then market prevailing prices, or a combination of both, at our election, provided that (i) Lonza had the right to receive up to 25 % of pre-IND payments in shares of our common stock, up to a maximum of $ 2.5 million, and (ii) we had the right to issue no more than $ 10.0 million of pre-IND payments in shares of our common stock. In April 2021, we reached the Initial Cash Cap and notified Lonza that we would be exercising our option to issue approximately $ 10.0 million in shares of our common stock as payment for a portion of pre-IND payments due April 30, 2021. In June 2021, we issued 399,680 shares of our common stock to Lonza at a price of $ 25.02 per share to pay for $ 10.0 million of the pre-IND payments due April 30, 2021. In October 2018, we entered into a second development and manufacturing services agreement with Lonza (the “Lonza 2018 DMSA,” and together with the Lonza DMSA, the “Lonza Agreements”), pursuant to which Lonza is obligated to perform services including manufacturing process development and the manufacture and supply of VAX-24 finished drug product. In April 2022, we entered into a master services agreement for drug product development and manufacturing (the "Master Services Agreement") with Lonza effective as of March 22, 2022, pursuant to which Lonza will perform manufacturing process development and clinical manufacture and supply of our proprietary pneumococcal conjugate vaccine. Unless terminated earlier, the Master Services Agreement will remain in place for a period of five years. Either party may terminate the Master Services Agreement for any reason with 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 Master Services Agreement (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 Master Services Agreement upon an extended force majeure event. Upon expiration and/or termination of the Master Services Agreement and/or any purchase order, we will pay Lonza for all services rendered, all costs incurred, all unreimbursed capital equipment and any cancellation fees. Under the Lonza Agreements, we will pay Lonza agreed-upon fees for Lonza’s performance of manufacturing services and reimburse Lonza for its out-of-pocket costs for purchases of raw materials, as well as a customary procurement and handling fee. Each Lonza Agreement is managed by a steering committee and any dispute at the steering committee will be resolved by senior executives of the parties. 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 September 30, 2022, we had the following amounts due 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 our 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) Remainder of 2022 $ 40,156 2023 40,837 Total non-cancelable purchase commitments due to our key manufacturing partners $ 80,993

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2022
Equity [Abstract]
Common Stock	7. 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 60,572,692 and 53,031,978 shares were issued and outstanding as of September 30, 2022 and December 31, 2021, 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 of directors. As of September 30, 2022 and December 31, 2021 , no dividends had 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 “ATM Sales Agreement”) with Jefferies LLC (“Jefferies”), which provides that, upon the terms and subject to the conditions and limitations set forth in the 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. 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 ATM Sales Agreement; however, we are not obligated to make any sales of common stock. As of September 30, 2022 , we have sold 4,383,810 shares of our common stock under the ATM Sales Agreement at an average price of $ 25.56 per share for aggregate gross proceeds of $ 112.0 million ($ 108.7 million net of commissions and offering expenses). In January 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, t he underwriters exercised their option to purchase an additional 750,000 shares of common stock. In aggregate, we received approximately $ 107.6 million in net proceeds after deducting underwriting discounts and commissions and other offering expenses payable by us. Common stock reserved for future issuance under the 2020 Equity Incentive Plan (the “2020 Plan”) and the 2014 Equity Incentive Plan (the “2014 Plan”) was as follows, and excludes 62,382 shares issued outside of the 2014 Plan and 2020 Plan: September 30, December 31, 2022 2021 Options issued and outstanding 7,595,417 5,295,007 Restricted stock units outstanding 420,167 — Shares available for future stock option grants 5,598,707 6,104,756 Total 13,614,291 11,399,763 Refer to Note 14, "Subsequent Events" for details of our underwritten public offering that was closed subsequent to September 30, 2022.

Pre-Funded Warrants

Pre-Funded Warrants	9 Months Ended
	Sep. 30, 2022
Equity [Abstract]
Pre-Funded Warrants	8. P re-Funded Warrants In connection with our underwritten public offering in January 2022, 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. Each pre-funded warrant has an exercise price of $ 0.001 per share. The public offering price for the pre-funded warrants was equal to the public offering price of our common stock, less the $ 0.001 exercise price of each pre-funded warrant and was recorded as a component of stockholders' equity within additional paid-in-capital. The pre-funded warrants will be 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 holder of the pre-funded warrants may also satisfy its 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 9.99 % of the number of shares of our common stock outstanding immediately after giving effect to the exercise; or (ii) the combined voting power of our securities beneficially owned by such holder (together with its affiliates) to exceed 9.99 % of the combined voting power of all of our securities outstanding immediately after giving effect to the exercise, 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 September 30, 2022 , no shares underlying the pre-funded warrants had been exercised. Refer to Note 14, "Subsequent Events" for details of our underwritten public offering that was closed subsequent to September 30, 2022.

Equity Incentive Plans

Equity Incentive Plans	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Equity Incentive Plans	9. Equity Incentive Plans 2020 and 2014 Equity Incentive Plans In June 2020, our board of directors 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 will be automatically increased on the first day of each calendar year during the ten-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 determined by our board of directors. Effective January 1, 2022, the number of shares of common stock available under the 2020 Plan increased by 2,651,598 shares pursuant to the evergreen provision. As of September 30, 2022, an aggregate of 5,598,707 shares of common stock were available for issuance under 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. As of September 30, 2022, 3,330,419 shares and 4,685,165 shares of common stock were subject to outstanding options and RSUs under the 2014 Plan and 2020 Plan, respectively. 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 condensed balance sheet and is reclassified to common stock and additional paid-in capital as such shares vest. At September 30, 2022 and December 31, 2021 , 4,632 and 7,410 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 September 30, 2022 and December 31, 2021 were both less than $ 0.1 million and were recorded in other liabilities. Stock Options and Restricted Stock Units Activity Stock options and RSUs activity under our 2020 Plan and 2014 Plan, which excludes options to purchase 62,382 shares granted outside of the 2020 Plan and 2014 Plan, was as follows: Options Outstanding Stock Options and Restricted Stock Units Activity Options and Number Weighted- Weighted- Aggregate Balances — December 31, 2021 6,104,756 5,295,007 $ 9.30 Additional shares authorized 2,651,598 — Options granted ( 2,866,831 ) 2,866,831 $ 24.37 Options exercised 385 (1) ( 390,852 ) $ 6.06 Options forfeited 175,569 ( 175,569 ) $ 26.14 Restricted stock units granted ( 526,886 ) Restricted stock units withheld 32,626 Restricted stock units forfeited 27,490 Balances — September 30, 2022 5,598,707 7,595,417 $ 14.76 8.03 $ 74,139 Vested and expected to vest — September 30, 2022 7,595,417 $ 14.76 8.03 $ 74,139 Exercisable at September 30, 2022 3,288,706 $ 7.10 6.76 $ 56,189 (1) Net exercise – shares returned to the Plan. During the three months ended September 30, 2022 and 2021 , 222,358 and 125,583 shares of stock options, respectively, were exercised for cash at a weighted-average price per share of $ 7.90 and $ 3.91 , respectively. The weighted-average grant date fair value of options granted for the three months ended September 30, 2022 and 2021 was $ 18.01 and $ 17.00 , respectively. The intrinsic value of the stock options exercised was $ 4.0 million and $ 2.5 mi llion for the three months ended September 30, 2022 and 2021, respectively. During the nine months ended September 30, 2022 and 2021 , 390,467 and 578,194 shares of stock options, respectively, were exercised for cash at a weighted-average price per share of $ 6.06 and $ 2.50 , respectively. The weighted-average grant date fair value of options granted for the nine months ended September 30, 2022 and 2021 was $ 16.39 and $ 14.37 , respectively. The intrinsic value of the stock options exercised was $ 7.4 million and $ 12.4 million for the nine months ended September 30, 2022 and 2021, respectively. In March 2022, our board of directors 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 nine months ended September 30, 2022 was as follows: Shares Weighted- Unvested at December 31, 2021 — $ — Granted 526,886 24.51 Vested and released ( 79,229 ) 24.79 Cancelled ( 27,490 ) 24.15 Unvested at September 30, 2022 420,167 $ 24.48 The weighted-average grant date fair value of RSUs granted during the three and nine months ended September 30, 2022 was $ 27.50 and $ 24.51 , respectively. The aggregate fair value of unvested RSU is calculated using the closing price of our common stock on the grant date. As of September 30, 2022 , the unrecognized stock-based compensation cost of unvested RSUs was $ 9.6 million, which is expected to be recognized over a weighted-average period of 3.1 years. 2020 Employee Stock Purchase Plan In June 2020, our board of directors 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 will be automatically increased on the first day of each calendar year during the ten-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 st of the preceding calendar year or such lesser amount as determined by our board of directors. Effective January 1, 2022, the number of shares of common stock available under the 2020 ESPP increased by 530,319 shares pursuant to the evergreen provision. As of September 30, 2022 , 1,564,144 shares of common stock were available for issuance under the 2020 ESPP. Stock-based Compensation We estimated the fair value of employee stock options using the Black-Scholes option-pricing model for the three and nine months ended September 30, 2022 and 2021 using the following weighted-average assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Fair Value Assumptions Expected volatility 80.4 % - 80.6 % 81.2 % - 81.8 % 78.1 % - 81.2 % 81.0 % - 82.5 % Expected dividend yield 0 % 0 % 0 % 0 % Expected term (in years) 5.5 5.4 5.4 - 5.5 5.4 - 5.5 Risk-free interest rate 2.7 % - 4.0 % 0.8 % - 1.1 % 1.6 % - 4.0 % 0.5 % - 1.1 % We estimated the fair value of shares under the 2020 ESPP using the Black-Scholes option-pricing model for the three and nine months ended September 30, 2022 and 2021 using the following weighted-average assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Fair Value Assumptions Expected volatility 78.8 % - 82.0 % 79.6 % - 88.8 % 78.8 % - 97.5 % 79.6 % - 126.3 % Expected dividend yield 0 % 0 % 0 % 0 % Expected term (in years) 0.5 - 2.0 0.5 - 2.0 0.5 - 2.0 0.5 - 2.0 Risk-free interest rate 1.6 % - 2.7 % 0.0 % - 0.2 % 0.1 % - 2.7 % 0.0 % - 0.2 % We recorded total stock-based compensation expense for the three and nine months ended September 30, 2022 and 2021 related to the 2014 Plan, the 2020 Plan and the 2020 ESPP in the condensed statements of operations and allocated the amounts as follows: Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 (in thousands) (in thousands) Research and development $ 2,682 $ 1,023 $ 6,804 $ 2,688 General and administrative 3,966 1,914 9,837 4,883 Total $ 6,648 $ 2,937 $ 16,641 $ 7,571

Funding Arrangement

Funding Arrangement	9 Months Ended
	Sep. 30, 2022
Funding Arrangement [Abstract]
Funding Arrangement	10. Funding Arrangement In July 2019, we received a cost-reimbursement research award from CARB-X, a public-private partnership funded under a Cooperative Agreement from Assistant Secretary for Preparedness and Response/Biomedical Advanced Research and Development Authority (“BARDA”) and by awards from Wellcome Trust, Germany’s Federal Ministry of Education and Research, the United Kingdom Global Antimicrobial Resistance Innovation Fund and the Bill & Melinda Gates Foundation. In connection with this funding, we entered into a cost-reimbursement sub-award agreement with the Trustees of Boston University, the administrator of the program. The initial award provided the potential for funding up to four years to develop a universal vaccine to prevent infections caused by Group A Strep bacteria, which include pharyngitis, impetigo and necrotizing fasciitis. The initial award committed initial funding of up to $ 1.6 million for our VAX-A1 program and, subject to a CARB-X decision to extend the options, up to $ 15.1 million in total funding available upon achievement of development milestones over the next four years . Specified research expenditures are reimbursable expenses associated with agreed-upon activities needed to advance the research project supported by the grant. These expenditures can include labor, laboratory supplies, travel, consulting and third-party vendor research and development support costs. In July 2020, the CARB-X agreement was amended with the initial funding amount increased from $ 1.6 million to $ 2.7 million. In December 2020, we reached the maximum CARB-X funding limit for this initial funding period, and subsequently submitted our funding proposal to CARB-X for the next period under our agreement. In April 2021, we received approval for the next phase of CARB-X development and executed the cost-reimbursement sub-award agreement with the Trustees of Boston University in August 2021. Pursuant to the agreement, the award committed additional funding of $ 3.2 million for IND-enabling activities and total potential funding of up to $ 29.7 million (including the current $ 3.2 million award and the prior $ 2.7 million award) upon the achievement of future VAX-A1 development milestones. In January 2022, CARB-X revised the parameters for the contribution of CARB-X funding and implemented maximum funding levels for all grant recipients. As a result, our total funding available upon achievement of development milestones through Phase 1 human clinical trials was revised from $ 29.7 million to $ 13.9 million. In April 2021, we received a cost-reimbursement research award from National Institutes of Health (“NIH”). In connection with this funding, we entered into a cost-reimbursement sub-award agreement with the University of Maryland, Baltimore, the administrator of the program. The award provides for potential funding up to five years totaling approximately $ 0.5 million to develop a vaccine to prevent infections caused by Shigella. 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 $ 0.2 million and $ 0.3 million of grant income under the CARB-X and Shigella awards and recorded the amounts in Other income (expense), net in the condensed statement of operations during the three months ended September 30, 2022 and 2021, respectively, and $ 1 million and $ 0.7 million during the nine months ended September 30, 2022 and 2021, respectively. A grant receivable of $ 0.7 million and $ 1.2 million representing unreimbursed, eligible costs incurred under the CARB-X and Shigella agreements was recorded and included in Prepaid expenses and other current assets in the condensed balance sheets as of September 30, 2022 and December 31, 2021 , respectively.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2022
Earnings Per Share [Abstract]
Net Loss Per Share	11. 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: Three Months Ended Nine Months Ended 2022 2021 2022 2021 Net loss (in thousands) $ ( 57,917 ) $ ( 26,615 ) $ ( 145,435 ) $ ( 71,514 ) Weighted-average shares outstanding used in computing net (1) 61,989,347 52,187,303 60,166,583 51,627,249 Net loss per share, basic and diluted $ ( 0.93 ) $ ( 0.51 ) $ ( 2.42 ) $ ( 1.39 ) (1) Includes shares of common stock into which pre-funded warrants may be exercised as of September 30, 3022 and does not include any pre-funded warrants issued subsequent to that date. See Note 8 - Pre-Funded Warrants. Potentially dilutive securities outstanding as of the periods presented below were excluded from the computation of diluted net loss per share for the three and nine months ended September 30, 2022 because including them would have been antidilutive: As of September 30, 2022 2021 Stock options 7,657,799 5,489,389 Restricted stock units 420,167 — Employee stock purchase plan shares 103,060 74,957 Total 8,181,026 5,564,346

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes In determining quarterly provisions for income taxes, we use the annual estimated effective tax rate applied to the actual year-to-date profit or loss, adjusted for discrete items arising in that period. Our annual estimated effective tax rate differs from the U.S. federal statutory rate primarily as a result of state taxes and changes in our valuation allowance against our deferred tax assets. For all periods presented, we have incurred net pre-tax losses in the United States. During the three and nine months ended September 30, 2022, there were no material changes to our unrecognized tax benefits, and we do not expect to have any significant changes to unrecognized tax benefits through the end of the fiscal year. For the three and nine months ended September 30, 2022 , we reported zero tax provision. We do not have any tax audits or other issues pending.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2022
Related Party Transactions [Abstract]
Related Party Transactions	13. Related Party Transactions We have an ongoing relationship with Sutro Biopharma. 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 a 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 , which was amended in February 2021 (the “Sutro Biopharma Supply Agreement”). As of June 2, 2021, Sutro Biopharma was no longer considered as 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 expenses related to the Sutro Biopharma Supply Agreement of $ 0 for both the three months ended September 30, 2022 and 2021 , and $ 0 and $ 2.4 million for the nine months ended September 30, 2022 and 2021 , respectively.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2022
Disclosure Text Block [Abstract]
Subsequent Events	14. Subsequent Events Announcement of Positive Topline Results from VAX-24 Phase 1/2 Clinical Proof-of-Concept Study in Adults 18-65 Years of Age On October 24, 2022, we announced positive topline results from the Phase 1/2 clinical proof-of-concept study evaluating the safety, tolerability and immunogenicity of VAX-24 in healthy adults aged 18-64. In this study, VAX-24 met the primary safety and tolerability objectives, demonstrating a safety profile similar to Prevnar 20™ (PCV20) for all doses studied. In the study, VAX-24 met or exceeded the established regulatory immunogenicity standards for all 24 serotypes at the conventional 2.2mcg dose, which the we intend to move forward into a Phase 3 program. At this dose, VAX-24 met the standard opsonophagocytic activity response non-inferiority criteria for all 20 serotypes common with PCV20, of which 16 achieved higher immune responses. Additionally, at all three doses, VAX-24 met the standard superiority criteria for all four serotypes unique to VAX-24. These four incremental serotypes cover 10-15 percent of strains causing invasive pneumococcal disease over the current standard-of-care in adults. October 2022 Underwritten Public Offering On October 28, 2022, we completed an underwritten public offering in which we issued 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 approximately $ 650.7 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.

Basis of Presentation and Sum_2

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation These condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or U.S. GAAP, and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and footnote disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted in accordance with such rules and regulations.
Unaudited Interim Condensed Financial Statements	Unaudited Interim Condensed Financial Statements The condensed balance sheet as of September 30, 2022, the condensed statements of operations, comprehensive loss and stockholders’ equity for the three and nine months ended September 30, 2022 and 2021 and the condensed statements of cash flows for the nine months ended September 30, 2022 and 2021 are unaudited. The unaudited interim condensed financial statements have been prepared on the same basis as the audited annual financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair statement of our financial information. The financial data disclosed in the footnotes to the condensed financial statements related to the three and nine months ended September 30, 2022 and 2021 are also unaudited. The results of operations for the three and nine months ended September 30, 2022 are not necessarily indicative of the results to be expected for the year ending December 31, 2022 or for any other future annual or interim period. These interim condensed financial statements should be read in conjunction with our audited financial statements and related notes thereto for the year ended December 31, 2021 included in our Annual Report on Form 10-K filed with the SEC on February 28, 2022.
Use of Estimates	Use of Estimates The preparation of 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 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 determination of our 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.
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 and cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts and commercial paper and are stated at their fair values. Restricted cash consists of a standby letter of credit, which was issued in the first quarter of 2021, that serves as collateral for the lease agreement for our new corporate headquarters. Cash, cash equivalents and restricted cash as reported within the condensed balance sheets that total to the same amounts shown in the condensed statement of cash flows are as follows: September 30, December 31, 2022 2021 (in thousands) Cash and cash equivalents $ 278,401 $ 68,985 Restricted cash 871 871 Cash, cash equivalents and restricted cash $ 279,272 $ 69,856
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 condensed balance sheets at fair value. Unrealized gains and losses on these securities are included as a separate component of accumulated other comprehensive 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 condensed 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 income, and are recognized in our condensed consolidated statements of operations only if we sell or intend to sell the security before recovery of its cost basis.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted average of shares of common stock outstanding, including pre-funded warrants issued, during the period, without consideration for common stock equivalents. 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. Diluted net loss per share is the same as basic net loss per share since the effects of potentially dilutive securities are antidilutive given the net loss for each period presented.
Deferred Offering Costs	Deferred Offering Costs Deferred offering costs consist of fees and expenses incurred in connection with the sale of our common stock in equity transactions, including legal, accounting, printing and other issuance-related costs. Prior to the completion of such equity transactions, these deferred offering costs were included in Other assets on the condensed balance sheet. In connection with and as of the closing of such equity transactions, these costs were reclassified to Additional paid-in capital, representing a reduction to the gross proceeds. As of September 30, 2022 and December 31, 2021 , we recorded deferred offering costs of $ 0.2 million and $ 0.5 million, respectively, in Other assets on the condensed balance sheets.
Leases	Leases Under Financial Accounting Standards Board ("FASB") Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842) and its associated amendments (“ASC 842”), 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 September 30, 2022, our lease population consisted of real estate operating leases. As of September 30, 2022 , we did no t have 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 condensed balance sheet. 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 us. 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 and lease 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 condensed balance sheets.
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 and 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 condensed balance sheets. 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 our suppliers. We source our critical raw materials from a sole source supplier, Sutro Biopharma, Inc. (“Sutro Biopharma”). We also use one contract manufacturing organization (“CMO”), Lonza Ltd. (“Lonza”), to handle most of our manufacturing activities. If we were to experience disruptions in raw materials supplied by Sutro Biopharma, 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 clinical or preclinical stages of 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 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; our ability to obtain additional capital to finance our operations; our ability to obtain, maintain and protect our intellectual property 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 Quarterly Report on Form 10-Q.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In November 2021, the FASB issued ASU 2021-10, Government Assistance (Topic 832): Disclosure by Business Entities about Government Assistance , which requires disclosures about transactions with a government entity that are accounted for by applying a grant or contribution accounting model by analogy to other accounting guidance, such as a grant model within International Accounting Standard 20, Accounting for Government Grants and Disclosure of Government Assistance (Subtopic 958-605), Not-For-Profit Entities - Revenue Recognition . The required disclosures include (i) the nature of the transaction and the related accounting policy used to account for the transaction, (ii) the financial statement line items that are affected by the transactions and (iii) the significant terms and conditions of the transactions, including commitments and contingencies. This standard is effective for annual periods beginning after December 15, 2021, with early adoption and retrospective or prospective application permitted. This standard is effective for us on January 1, 2022 and only impacts annual financial statement footnote disclosures. In Note 10, "Funding Arrangement," we included disclosures on our cost-reimbursement research award from Combating Antibiotic Resistant Bacteria Biopharmaceutical Accelerator ("CARB-X"). We have adopted this standard as required by the effective date. The adoption of this standard did not have a material impact on our financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments and has subsequently issued related amendments, collectively referred to as “Topic 326.” Topic 326 requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions and reasonable and supportable forecasts that affect collectability. Topic 326 also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. We have adopted this standard as required by the effective date on January 1, 2022. The adoption of this standard did not have a material impact on our financial statements.

Basis of Presentation and Sum_3

Basis of Presentation and Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Schedule of Cash, Cash Equivalents And Restricted Cash	Cash, cash equivalents and restricted cash as reported within the condensed balance sheets that total to the same amounts shown in the condensed statement of cash flows are as follows: September 30, December 31, 2022 2021 (in thousands) Cash and cash equivalents $ 278,401 $ 68,985 Restricted cash 871 871 Cash, cash equivalents and restricted cash $ 279,272 $ 69,856

Fair Value Measurements and F_2

Fair Value Measurements and Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2022
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 September 30, 2022 and December 31, 2021: September 30, 2022 Fair Value Amortized Gross Gross Fair Assets (in thousands) Cash and cash equivalents: Cash Level 1 $ 168,010 $ — $ — $ 168,010 Money market funds Level 1 29,927 — — 29,927 U.S. Treasury securities Level 1 — — — — Commercial paper Level 2 36,561 — ( 6 ) 36,555 U.S. government agency securities Level 2 43,903 6 — 43,909 Total cash and cash equivalents 278,401 6 ( 6 ) 278,401 Investments: U.S. Treasury securities Level 1 27,890 — ( 161 ) 27,729 Commercial paper Level 2 23,720 — ( 16 ) 23,704 Corporate debt Level 2 21,096 — ( 275 ) 20,821 Asset-backed securities Level 2 3,252 — ( 4 ) 3,248 U.S. government agency securities Level 2 12,501 — ( 201 ) 12,300 Total investments 88,459 — ( 657 ) 87,802 Total assets measured at fair value $ 366,860 $ 6 $ ( 663 ) $ 366,203 December 31, 2021 Fair Value Amortized Gross Gross Fair Assets (in thousands) Cash and cash equivalents: Cash Level 1 $ 27,834 $ — $ — $ 27,834 Money market funds Level 1 17,555 — — 17,555 Commercial paper Level 2 23,597 — ( 1 ) 23,596 Total cash and cash equivalents 68,986 — ( 1 ) 68,985 Investments: U.S. Treasury securities Level 1 45,290 — ( 73 ) 45,217 Commercial paper Level 2 61,941 — ( 22 ) 61,919 Corporate debt Level 2 58,498 — ( 74 ) 58,424 Asset-backed securities Level 2 13,899 — ( 25 ) 13,874 U.S. government agency securities Level 2 24,714 — ( 46 ) 24,668 Total investments 204,342 — ( 240 ) 204,102 Total assets measured at fair value $ 273,328 $ — $ ( 241 ) $ 273,087
Schedule of Contractual Maturities of Investments	The following table presents the contractual maturities of our investments as of September 30, 2022 (in thousands): September 30, 2022 Fair Value Due in less than one year $ 83,825 Due in one to five years 3,977 Total $ 87,802

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	9 Months Ended
	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net as of September 30, 2022 and December 31, 2021 consisted of the following: September 30, December 31, 2022 2021 (in thousands) Furniture and equipment $ 1,608 $ 1,619 Computers and computer software 416 430 Lab equipment 11,986 9,453 Leasehold improvements 1,352 — Total property and equipment 15,362 11,502 Less: accumulated depreciation and amortization ( 5,415 ) ( 3,548 ) Property and equipment, net $ 9,947 $ 7,954
Schedule of Accrued Expenses	Accrued expenses as of September 30, 2022 and December 31, 2021 consisted of the following September 30, December 31, 2022 2021 (in thousands) Clinical studies $ 3,379 $ 453 Other research and development 8,718 4,676 Other accrued expenses 1,581 3,658 Total $ 13,678 $ 8,787

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2022
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): Three Months Ended Nine Months Ended September 30, September 30, September 30, September 30, 2022 2021 2022 2021 Cash paid for operating lease liabilities $ 1,631 $ 350 $ 3,743 $ 920 Operating lease right-of-use assets 22,887 307 Current operating lease liabilities $ 6,426 $ 613 Non-current operating lease liabilities 13,356 553 Total lease liabilities $ 19,782 $ 1,166 Weighted-average remaining lease term (in years) 3.04 0.32 Weighted-average discount rate 7.6 % 7.2 %
Schedule of Maturities of Lease Liabilities	Maturities of lease liabilities as of September 30, 2022 were as follows: Years ending December 31, (in thousands) Remainder of 2022 $ 1,631 2023 6,684 2024 6,850 2025 7,022 Thereafter — Total future undiscounted lease payments 22,187 Less: Imputed interest ( 2,405 ) Total lease liabilities $ 19,782 Future minimum payments required under operating leases as of December 31, 2021 were as follows: Years ending December 31, (in thousands) 2022 (1) $ ( 105 ) 2023 6,639 2024 6,805 2025 6,976 Thereafter — Total future undiscounted lease payments 20,315 Less: Imputed interest ( 3,532 ) Total lease liabilities $ 16,783 (1) Maturities for 2022 are net of lease incentives of $ 0.9 million allocated to the Palo Alto office.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Schedule of Non-cancelable Purchase Commitments Related to Raw Materials	As of September 30, 2022, we had the following amounts due 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 our 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) Remainder of 2022 $ 40,156 2023 40,837 Total non-cancelable purchase commitments due to our key manufacturing partners $ 80,993

Common Stock (Tables)

Common Stock (Tables)	9 Months Ended
	Sep. 30, 2022
Equity [Abstract]
Schedule of Common Stock Shares Reserved for Future Issuance	Common stock reserved for future issuance under the 2020 Equity Incentive Plan (the “2020 Plan”) and the 2014 Equity Incentive Plan (the “2014 Plan”) was as follows, and excludes 62,382 shares issued outside of the 2014 Plan and 2020 Plan: September 30, December 31, 2022 2021 Options issued and outstanding 7,595,417 5,295,007 Restricted stock units outstanding 420,167 — Shares available for future stock option grants 5,598,707 6,104,756 Total 13,614,291 11,399,763 Refer to Note 14, "Subsequent Events" for details of our underwritten public offering that was closed subsequent to September 30, 2022.

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	9 Months Ended
	Sep. 30, 2022
Nonvested Restricted Stock Shares Activity	RSU activity for the nine months ended September 30, 2022 was as follows: Shares Weighted- Unvested at December 31, 2021 — $ — Granted 526,886 24.51 Vested and released ( 79,229 ) 24.79 Cancelled ( 27,490 ) 24.15 Unvested at September 30, 2022 420,167 $ 24.48
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 three and nine months ended September 30, 2022 and 2021 using the following weighted-average assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Fair Value Assumptions Expected volatility 80.4 % - 80.6 % 81.2 % - 81.8 % 78.1 % - 81.2 % 81.0 % - 82.5 % Expected dividend yield 0 % 0 % 0 % 0 % Expected term (in years) 5.5 5.4 5.4 - 5.5 5.4 - 5.5 Risk-free interest rate 2.7 % - 4.0 % 0.8 % - 1.1 % 1.6 % - 4.0 % 0.5 % - 1.1 %
2020 Plan and 2014 Plan
Summary of Activity Under Stock Option Plans	Stock options and RSUs activity under our 2020 Plan and 2014 Plan, which excludes options to purchase 62,382 shares granted outside of the 2020 Plan and 2014 Plan, was as follows: Options Outstanding Stock Options and Restricted Stock Units Activity Options and Number Weighted- Weighted- Aggregate Balances — December 31, 2021 6,104,756 5,295,007 $ 9.30 Additional shares authorized 2,651,598 — Options granted ( 2,866,831 ) 2,866,831 $ 24.37 Options exercised 385 (1) ( 390,852 ) $ 6.06 Options forfeited 175,569 ( 175,569 ) $ 26.14 Restricted stock units granted ( 526,886 ) Restricted stock units withheld 32,626 Restricted stock units forfeited 27,490 Balances — September 30, 2022 5,598,707 7,595,417 $ 14.76 8.03 $ 74,139 Vested and expected to vest — September 30, 2022 7,595,417 $ 14.76 8.03 $ 74,139 Exercisable at September 30, 2022 3,288,706 $ 7.10 6.76 $ 56,189 (1) Net exercise – shares returned to the Plan.
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 three and nine months ended September 30, 2022 and 2021 using the following weighted-average assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 Fair Value Assumptions Expected volatility 78.8 % - 82.0 % 79.6 % - 88.8 % 78.8 % - 97.5 % 79.6 % - 126.3 % Expected dividend yield 0 % 0 % 0 % 0 % Expected term (in years) 0.5 - 2.0 0.5 - 2.0 0.5 - 2.0 0.5 - 2.0 Risk-free interest rate 1.6 % - 2.7 % 0.0 % - 0.2 % 0.1 % - 2.7 % 0.0 % - 0.2 %
2014 Plan, 2020 Plan and 2020 ESPP
Summary of Stock-based Compensation Expense	We recorded total stock-based compensation expense for the three and nine months ended September 30, 2022 and 2021 related to the 2014 Plan, the 2020 Plan and the 2020 ESPP in the condensed statements of operations and allocated the amounts as follows: Three Months Ended September 30, Nine Months Ended September 30, 2022 2021 2022 2021 (in thousands) (in thousands) Research and development $ 2,682 $ 1,023 $ 6,804 $ 2,688 General and administrative 3,966 1,914 9,837 4,883 Total $ 6,648 $ 2,937 $ 16,641 $ 7,571

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2022
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: Three Months Ended Nine Months Ended 2022 2021 2022 2021 Net loss (in thousands) $ ( 57,917 ) $ ( 26,615 ) $ ( 145,435 ) $ ( 71,514 ) Weighted-average shares outstanding used in computing net (1) 61,989,347 52,187,303 60,166,583 51,627,249 Net loss per share, basic and diluted $ ( 0.93 ) $ ( 0.51 ) $ ( 2.42 ) $ ( 1.39 ) (1) Includes shares of common stock into which pre-funded warrants may be exercised as of September 30, 3022 and does not include any pre-funded warrants issued subsequent to that date. See Note 8 - Pre-Funded Warrants.
Schedule of Potentially Dilutive Securities Excluded From Computation of Diluted Net Loss Per Share	Potentially dilutive securities outstanding as of the periods presented below were excluded from the computation of diluted net loss per share for the three and nine months ended September 30, 2022 because including them would have been antidilutive: As of September 30, 2022 2021 Stock options 7,657,799 5,489,389 Restricted stock units 420,167 — Employee stock purchase plan shares 103,060 74,957 Total 8,181,026 5,564,346

Basis of Presentation and Sum_4

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2022 USD ($) Lease	Dec. 31, 2021 USD ($)
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Number of finance lease | Lease	0
Other Assets
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Deferred offering costs | $	$ 0.2	$ 0.5

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	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Cash and cash equivalents	$ 278,401	$ 68,985
Restricted Cash	871	871
Cash, cash equivalents and restricted cash	$ 279,272	$ 69,856	$ 112,915	$ 386,200

Fair Value Measurements and F_3

Fair Value Measurements and Fair Value of Financial Instruments - Additional Information (Details) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2022 USD ($) Security	Sep. 30, 2022 USD ($) Security	Dec. 31, 2021 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	$ 0
Fair value assets transferred out of level 3	0	0	0
Fair value liabilities transferred into level 3	0	0	0
Fair value liabilities transferred out of level 3	$ 0	$ 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	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	Sep. 30, 2022	Dec. 31, 2021
Assets:
Investments, Fair Value	$ 87,802
Fair Value, Recurring
Assets:
Cash and cash equivalents, Amortized Cost	278,401	$ 68,986
Cash and cash equivalents, Gross Unrealized Gains	6
Cash and cash equivalents, Gross Unrealized Losses	(6)	(1)
Cash and cash equivalents, Fair Value	278,401	68,985
Investments, Amortized Cost	88,459	204,342
Investments, Gross Unrealized Losses	(657)	(240)
Investments, Fair Value	87,802	204,102
Total assets measured at fair value, Amortized Cost	366,860	273,328
Total assets measured at fair value, Gross Unrealized Gains	6
Total assets measured at fair value, Gross Unrealized Losses	(663)	(241)
Total assets measured at fair value, Fair Value	366,203	273,087
Fair Value, Recurring | Cash | Level 1
Assets:
Cash and cash equivalents, Amortized Cost	168,010	27,834
Cash and cash equivalents, Fair Value	168,010	27,834
Fair Value, Recurring | Money Market Funds | Level 1
Assets:
Cash and cash equivalents, Amortized Cost	29,927	17,555
Cash and cash equivalents, Fair Value	29,927	17,555
Fair Value, Recurring | U.S. Treasury Securities | Level 1
Assets:
Cash and cash equivalents, Amortized Cost	0
Cash and cash equivalents, Fair Value	0
Investments, Amortized Cost	27,890	45,290
Investments, Gross Unrealized Losses	(161)	(73)
Investments, Fair Value	27,729	45,217
Fair Value, Recurring | Commercial Paper | Level 2
Assets:
Cash and cash equivalents, Amortized Cost	36,561	23,597
Cash and cash equivalents, Gross Unrealized Losses	(6)	(1)
Cash and cash equivalents, Fair Value	36,555	23,596
Investments, Amortized Cost	23,720	61,941
Investments, Gross Unrealized Losses	(16)	(22)
Investments, Fair Value	23,704	61,919
Fair Value, Recurring | U.S. Government Agency Securities | Level 2
Assets:
Cash and cash equivalents, Amortized Cost	43,903
Cash and cash equivalents, Gross Unrealized Gains	6
Cash and cash equivalents, Gross Unrealized Losses	0
Cash and cash equivalents, Fair Value	43,909
Investments, Amortized Cost	12,501	24,714
Investments, Gross Unrealized Losses	(201)	(46)
Investments, Fair Value	12,300	24,668
Fair Value, Recurring | Corporate Debt | Level 2
Assets:
Investments, Amortized Cost	21,096	58,498
Investments, Gross Unrealized Losses	(275)	(74)
Investments, Fair Value	20,821	58,424
Fair Value, Recurring | Asset-backed Securities | Level 2
Assets:
Investments, Amortized Cost	3,252	13,899
Investments, Gross Unrealized Losses	(4)	(25)
Investments, Fair Value	$ 3,248	$ 13,874

Fair Value Measurements and F_5

Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Contractual Maturities of Investments (Details) $ in Thousands	Sep. 30, 2022 USD ($)
Fair Value Disclosures [Abstract]
Due in less than one year	$ 83,825
Due in one to five years	3,977
Total	$ 87,802

Balance Sheet Details - Schedul

Balance Sheet Details - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Property Plant And Equipment [Line Items]
Total property and equipment	$ 15,362	$ 11,502
Less: accumulated depreciation and amortization	(5,415)	(3,548)
Property and equipment, net	9,947	7,954
Furniture and Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	1,608	1,619
Computers and Computer Software
Property Plant And Equipment [Line Items]
Total property and equipment	416	430
Lab Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	11,986	9,453
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 1,352	$ 0

Balance Sheet Details - Additio

Balance Sheet Details - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 0.7	$ 0.5	$ 1.9	$ 1.3

Balance Sheet Details - Sched_2

Balance Sheet Details - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Accrued Liabilities, Current [Abstract]
Clinical studies	$ 3,379	$ 453
Other research and development	8,718	4,676
Other accrued expenses	1,581	3,658
Total	$ 13,678	$ 8,787

Leases - Additional Information

Leases - Additional Information (Details) $ in Millions	1 Months Ended					3 Months Ended		9 Months Ended
	Feb. 28, 2022	Jan. 31, 2021 RenewalOption	Nov. 30, 2020	Jul. 31, 2019	Jul. 31, 2016 RenewalOption	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)
Lessee Lease Description [Line Items]
Operating leases, rent expense recognized | $						$ 1.9	$ 1	$ 6	$ 1.9
Headquarters Facility
Lessee Lease Description [Line Items]
Operating lease, agreement term					5 years
Operating lease, commencement date					Sep. 01, 2016
Lease expiration date					Aug. 31, 2021
Operating lease, renewal option					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 prior 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 as a result of growth in personnel and lab space requirements. 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
Lease Termination Date	Feb. 12, 2022
New Corporate Headquarters Facility
Lessee Lease Description [Line Items]
Lease expiration date		Dec. 31, 2025
Operating lease, renewal term		60 months
Operating lease, extended term		60 days
Number of renewal options		2
Palo Alto
Lessee Lease Description [Line Items]
Operating lease, extended maturity date		Mar. 03, 2022

Leases - Schedule of Informatio

Leases - Schedule of Information Related to ROU Assets and Lease Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Leases [Abstract]
Cash paid for operating lease liabilities	$ 1,631	$ 350	$ 3,743	$ 920
Operating lease right-of-use assets	22,887	307	22,887	307	$ 27,958
Current operating lease liabilities	6,426	613	6,426	613	5,276
Non-current operating lease liabilities	13,356	553	13,356	553	11,507
Total lease liabilities	$ 19,782	$ 1,166	$ 19,782	$ 1,166	$ 16,783
Weighted-average remaining lease term (in years)	3 years 14 days	3 months 25 days	3 years 14 days	3 months 25 days
Weighted-average discount rate	7.60%	7.20%	7.60%	7.20%

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021		Sep. 30, 2021
Leases [Abstract]
Remainder of 2022	$ 1,631	$ (105)	[1]
2023	6,684	6,639
2024	6,850	6,805
2025	7,022	6,976
Total future undiscounted lease payments	22,187	20,315
Less: Imputed interest	(2,405)	(3,532)
Total lease liabilities	$ 19,782	$ 16,783		$ 1,166
[1] Maturities for 2022 are net of lease incentives of $ 0.9 million allocated to the Palo Alto office.

Leases - Schedule of Maturiti_2

Leases - Schedule of Maturities of Lease Liabilities (Parenthetical) (Details) $ in Millions	Sep. 30, 2022 USD ($)
Palo Alto
Lessee Lease Description [Line Items]
Lease Incentives	$ 0.9

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - Lonza DMSA - USD ($)		1 Months Ended
	Jun. 30, 2018	Jun. 30, 2021	Apr. 30, 2021
Loss Contingencies [Line Items]
Percentage of defer payments agreed for completion			50%
Payments in equity, amount		$ 10,000,000
Amount recorded with respect to the potential future payments above the initial cash cap			$ 10,000,000
Number of common stock issued		399,680
Public offering price per share		$ 25.02
Maximum
Loss Contingencies [Line Items]
Payments in equity, percentage	25%
Payments in equity, amount	$ 2,500,000
Equity payment, upper limit	$ 10,000,000

Commitments and Contingencies_2

Commitments and Contingencies - Schedule Of non-cancelable purchase commitments related to raw materials - (Details) $ in Thousands	Sep. 30, 2022 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Remainder of 2022	$ 40,156
2023	40,837
Total non-cancelable purchase commitments due to our key manufacturing partners	$ 80,993

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		9 Months Ended		12 Months Ended
	Feb. 28, 2022	Jan. 31, 2022	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Jul. 31, 2021
Class Of Stock [Line Items]
Common stock, shares authorized			500,000,000		500,000,000
Common stock, par value per share			$ 0.001		$ 0.001
Common stock, shares issued			60,572,692		53,031,978
Common stock, shares outstanding			60,572,692		53,031,978
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			$ 95,238	$ 7,108
Equity incentive plan, shares issued			62,382
Over-Allotment Option
Class Of Stock [Line Items]
Shares issued		2,500,000
Common stock price per share		$ 20
Pre-funded warrants to purchase shares		2,500,000
Prefunded Warrants Price Per Share		$ 19.999
Underwriters' option to purchase additional share	750,000
Net proceeds from follow on offering	$ 107,600
ATM Sales Agreement | Jefferies LLC
Class Of Stock [Line Items]
Maximum commission percentage of gross proceeds from common stock sold						3%
Issuance of common stock, shares			4,383,810
Average price per share			$ 25.56
Aggregate gross proceeds from issuance of common stock			$ 112,000
Proceeds from issuance of stock, net of commission and offering expenses			$ 108,700
ATM Sales Agreement | Maximum | Jefferies LLC
Class Of Stock [Line Items]
Aggregate offering price						$ 150,000

Common Stock - Schedule of Comm

Common Stock - Schedule of Common Stock Shares Reserved for Future Issuance (Details) - 2020 Plan and 2014 Plan - shares	Sep. 30, 2022	Dec. 31, 2021
Class Of Stock [Line Items]
Common stock reserved for future issuances	13,614,291	11,399,763
Options Issued and Outstanding
Class Of Stock [Line Items]
Common stock reserved for future issuances	7,595,417	5,295,007
Restricted stock units outstanding
Class Of Stock [Line Items]
Common stock reserved for future issuances	420,167	0
Shares Available for Future Stock Option Grants
Class Of Stock [Line Items]
Common stock reserved for future issuances	5,598,707	6,104,756

Pre-Funded Warrants - Additiona

Pre-Funded Warrants - Additional Information (Details) - $ / shares	1 Months Ended
	Jan. 31, 2022	Sep. 30, 2022
Class Of Stock [Line Items]
Warrant exercised	0.001	0
Pre-funded warrants of common stock shares outstanding Immediately after effect to the exercise	9.99%
Combined voting power of securities outstanding immediately after effect to the exercise	9.99%
Increase or Decrease of Pre-funded Warrant Percentage Not Exceed	19.99%
Over-Allotment Option
Class Of Stock [Line Items]
Shares issued	2,500,000
Common stock price per share	$ 20
Pre-funded warrants to purchase shares	2,500,000
Prefunded Warrants Price Per Share	$ 19.999
Pre-funded warrant recorded as a component of stockholders' equity within additional paid-in-capital	$ 0.001

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended		9 Months Ended
	Jan. 01, 2021	Jun. 11, 2020	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	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			4,632		4,632		7,410
Options granted					62,382
Exercise of stock options (in shares)			222,358	125,583	390,467	578,194
Weighted-average price per share			$ 7.90	$ 3.91	$ 6.06	$ 2.50
Weighted-average grant date fair value of options granted			$ 18.01	$ 17	$ 16.39	$ 14.37
Intrinsic value of the stock options exercised			$ 4	$ 2.5	$ 7.4	$ 12.4
Number of restricted stock units vested					79,229
Restricted stock units outstanding
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
Vesting percentage for stock options granted, Six months thereafter		12.50%
Other Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period for stock options granted		3 years 6 months
Vesting percentage for stock options granted, Six months thereafter		12.50%
Weighted-average grant date fair value of options granted			$ 27.50		$ 24.51
Unrecognized stock-based compensation cost			$ 9.6		$ 9.6
Unrecognized cost expected to be recognized over a weighted-average period (in years)					3 years 1 month 6 days
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 outstanding		10,150,000
Percentage of outstanding number of shares		5%
Available for issuance of shares increased	2,651,598
Aggregate number of shares available for issuance			5,598,707		5,598,707
2020 Equity Incentive Plan | Restricted stock units outstanding
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares outstanding			4,685,165		4,685,165
2014 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares outstanding			3,330,419		3,330,419
2020 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares outstanding		650,000
Term of plan		10 years
Percentage of outstanding number of shares		1%
Available for issuance of shares increased	530,319
Aggregate number of shares available for issuance			1,564,144		1,564,144
Percentage of payroll deductions of eligible compensation		15%
Employees purchase shares of common stock of lower of fair market value		85%
Offering period		2 years
Purchase period		6 months
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		$ 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%
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%

Equity Incentive Plans - Summar

Equity Incentive Plans - Summary of Activity Under Stock Option Plans (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options, granted				62,382
Weighted-Average Exercise Price Per Share, Options exercised		$ 7.90	$ 3.91	$ 6.06	$ 2.50
2020 Plan and 2014 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options and Restricted Stock Units Available for Grant, Beginning Balance				6,104,756
Options and Restricted Stock Units Available for Grant, Additional shares authorized				2,651,598
Options and Restricted Stock Units Available for Grant, granted				(2,866,831)
Options and Restricted Stock Units Available for Grant, exercised	[1]			385
Options and Restricted Stock Units Available for Grant, forfeited				175,569
Options and Restricted Stock Units Available for Grant, Ending Balance		5,598,707		5,598,707
Number of Options, Beginning Balance				5,295,007
Number of Options, granted				2,866,831
Number of Options, exercised				(390,852)
Number of Options, forfeited				(175,569)
Number of Options, Ending Balance		7,595,417		7,595,417
Number of Options, Vested and expected to vest		7,595,417		7,595,417
Number of Options, Exercisable		3,288,706		3,288,706
Weighted-Average Exercise Price Per Share, Beginning Balance				$ 9.30
Weighted-Average Exercise Price Per Share, Options granted				24.37
Weighted-Average Exercise Price Per Share, Options exercised				6.06
Weighted-Average Exercise Price Per Share, Options forfeited				26.14
Weighted-Average Exercise Price Per Share, Ending Balance		$ 14.76		14.76
Weighted-Average Exercise Price Per Share, Vested and expected to vest		14.76		14.76
Weighted-Average Exercise Price Per Share, Exercisable		$ 7.10		$ 7.10
Weighted-Average Remaining Contractual Term (Years)				8 years 10 days
Weighted-Average Remaining Contractual Term (Years), Vested and expected to vest				8 years 10 days
Weighted-Average Remaining Contractual Term (Years), Exercisable				6 years 9 months 3 days
Aggregate Intrinsic Value		$ 74,139		$ 74,139
Aggregate Intrinsic Value, Vested and expected to vest		74,139		74,139
Aggregate Intrinsic Value, Exercisable		$ 56,189		$ 56,189
2020 Plan and 2014 Plan | Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options and Restricted Stock Units Available for Grant, granted				(526,886)
Options and Restricted Stock Units Available for Grant, forfeited				27,490
Restricted stock units withheld				32,626
[1] Net exercise – shares returned to the Plan.

Equity Incentive Plan - Nonvest

Equity Incentive Plan - Nonvested Restricted Stock Shares Activity (Details)	9 Months Ended
	Sep. 30, 2022 USD ($) shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Granted | shares	526,886
Vested and released | shares	(79,229)
Cancelled | shares	(27,490)
Unvested at September 30, 2022 | shares	420,167
Weighted average grant date fair value, granted | $	$ 24,510
Weighted average grant date fair value, cancelled | $	24,150
Weighted average grant date fair value, vested and released | $	24,790
Weighted average grant date fair value | $	$ 24,480

Equity Incentive Plans - Summ_2

Equity Incentive Plans - Summary of Estimated Fair Value of Employee Stock Options (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Fair Value Assumptions
Expected volatility, Minimum	80.40%	81.20%	78.10%	81%
Expected volatility, Maximum	80.60%	81.80%	81.20%	82.50%
Expected dividend yield	0%	0%	0%	0%
Expected term (in years)	5 years 6 months	5 years 4 months 24 days
Risk-free interest rate, Minimum	2.70%	0.80%	1.60%	0.50%
Risk-free interest rate, Maximum	4%	1.10%	4%	1.10%
Minimum
Fair Value Assumptions
Expected term (in years)			5 years 4 months 24 days	5 years 4 months 24 days
Maximum
Fair Value Assumptions
Expected term (in years)			5 years 6 months	5 years 6 months

Equity Incentive Plans - Summ_3

Equity Incentive Plans - Summary of Estimated Fair Value of Shares Under Employee Stock Purchase Plan (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Fair Value Assumptions
Expected volatility, Minimum	80.40%	81.20%	78.10%	81%
Expected volatility, Maximum	80.60%	81.80%	81.20%	82.50%
Expected dividend yield	0%	0%	0%	0%
Expected term (in years)	5 years 6 months	5 years 4 months 24 days
Risk-free interest rate, Minimum	2.70%	0.80%	1.60%	0.50%
Risk-free interest rate, Maximum	4%	1.10%	4%	1.10%
Minimum
Fair Value Assumptions
Expected term (in years)			5 years 4 months 24 days	5 years 4 months 24 days
Maximum
Fair Value Assumptions
Expected term (in years)			5 years 6 months	5 years 6 months
2020 Employee Stock Purchase Plan
Fair Value Assumptions
Expected volatility, Minimum	78.80%	79.60%	78.80%	79.60%
Expected volatility, Maximum	82%	88.80%	97.50%	126.30%
Expected dividend yield	0%	0%	0%	0%
Risk-free interest rate, Minimum	1.60%	0%	0.10%	0%
Risk-free interest rate, Maximum	2.70%	0.20%	2.70%	0.20%
2020 Employee Stock Purchase Plan | Minimum
Fair Value Assumptions
Expected term (in years)	6 months	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	2 years

Equity Incentive Plans - Summ_4

Equity Incentive Plans - Summary of Stock-based Compensation Expense (Details) - 2014 Plan, 2020 Plan and 2020 ESPP - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 6,648	$ 2,937	$ 16,641	$ 7,571
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	2,682	1,023	6,804	2,688
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 3,966	$ 1,914	$ 9,837	$ 4,883

Funding Arrangement - Additiona

Funding Arrangement - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended
	Apr. 30, 2021	Jul. 31, 2019	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Jan. 31, 2022	Dec. 31, 2021	Aug. 04, 2021	Jul. 31, 2020
Funding Arrangement [Line Items]
Grant income			$ 157	$ 299	$ 1,006	$ 677
Cost Reimbursement Sub-Award Agreement
Funding Arrangement [Line Items]
Funding period of award to develop universal vaccine to prevent infections caused by Group A Strep bacteria		4 years
Potential funding amount of award to develop vaccine to prevent shingella infections	$ 500
Grant income			200	$ 300	1,000	$ 700
Cost Reimbursement Sub-Award Agreement | Maximum
Funding Arrangement [Line Items]
Initial funding committed by award		$ 1,600
Total funding committed by award, available upon achievement of development milestones		$ 15,100
Potential funding period of award to develop vaccine to prevent shingella infections	5 years
CARB-X Agreement
Funding Arrangement [Line Items]
Additional funding committed by award									$ 3,200
Potential funding committed by award							$ 13,900
Grant receivable on unreimbursed, eligible costs incurred			$ 700		$ 700			$ 1,200
CARB-X Agreement | Maximum
Funding Arrangement [Line Items]
Initial funding committed by award										$ 2,700
Additional funding committed by award									3,200
Potential funding committed by award									$ 29,700
CARB-X Agreement | Minimum
Funding Arrangement [Line Items]
Initial funding committed by award										$ 1,600

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	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Earnings Per Share [Abstract]
Net loss (in thousands)	$ (57,917)	$ (26,615)	$ (145,435)	$ (71,514)
Weighted Average Number of Shares Outstanding, Basic	61,989,347	52,187,303	60,166,583	51,627,249
Weighted Average Number of Shares Outstanding, Diluted	61,989,347	52,187,303	60,166,583	51,627,249
Earnings Per Share, Basic	$ (0.93)	$ (0.51)	$ (2.42)	$ (1.39)
Earnings Per Share, Diluted	$ (0.93)	$ (0.51)	$ (2.42)	$ (1.39)

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	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	8,181,026	5,564,346
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	420,167	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	103,060	74,957
Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of diluted net loss per share	7,657,799	5,489,389

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Tax provision	$ 0	$ 0

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - Sutro Biopharma, Inc - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		9 Months Ended
	May 29, 2018	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
License Agreement
Related Party Transaction [Line Items]
Percentage of royalty payment on annual net sales of vaccine products for human health		4%		4%
Percentage of royalty payment on net sales of vaccine compositions for animal health		2%		2%
Supply Agreement
Related Party Transaction [Line Items]
Expenses related to agreement		$ 0	$ 0	$ 0	$ 2.4
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

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - Over-Allotment Option - USD ($) $ / shares in Units, $ in Millions		1 Months Ended
	Oct. 28, 2022	Feb. 28, 2022	Jan. 31, 2022
Subsequent Event [Line Items]
Shares issued			2,500,000
Underwriters' option to purchase additional share		750,000
Common stock price per share			$ 20
Pre-funded warrants to purchase shares			2,500,000
Prefunded Warrants Price Per Share			$ 19.999
Net proceeds from follow on offering		$ 107.6
Subsequent Event
Subsequent Event [Line Items]
Shares issued	17,812,500
Underwriters' option to purchase additional share	2,812,500
Common stock price per share	$ 32
Pre-funded warrants to purchase shares	3,750,000
Prefunded Warrants Price Per Share	$ 31.999
Net proceeds from follow on offering	$ 650.7