FORM 6-K SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Report of Foreign Private Issuer Pursuant to Rule 13s - 16 or 15d - 16 of the Securities Exchange Act of 1934 For the month of July 2006 Acambis plc (Translation of registrant's name into English) Peterhouse Technology Park 100 Fulbourn Road Cambridge CB1 9PT England (address of principal executive offices) (Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F Forms 20-F X Form 40-F Indicate by check mark whether the registrant by furnishing the information contained in this Form also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934). Yes No X (if "Yes" is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): 82- ). Enclosure: Update on MVA procurement Update on US Government MVA vaccine procurement process Cambridge, UK and Cambridge, Massachusetts - 26 July 2006 - Acambis plc ("Acambis") (LSE: ACM, NASDAQ: ACAM) provides an update on the US Government tender process relating to Modified Vaccinia Ankara ("MVA") attenuated smallpox vaccine. The Department of Health and Human Services ("HHS") of the US Government is seeking to procure up to 20 million doses of MVA vaccine and issued a Request for Proposals No. DHHS-ORDC-V&B-05-06 ("RFP3") in August 2005. Acambis, which is developing an MVA vaccine in partnership with Baxter Healthcare SA, submitted an initial response to RFP3 in October 2005 and has submitted further responses since then as part of the ongoing procurement process. HHS has issued an amendment to RFP3. This incorporates a revised pre-clinical and clinical testing requirement, following guidance received from the US Food and Drug Administration ("FDA"). It also extends the delivery period for usable MVA vaccine from 24 months to 60 months from contract award. Responses to the RFP3 amendment are to be provided to HHS by mid-August. Thereafter, it is expected that Final Proposal Revisions will be requested prior to contract award(s) being made. The revised testing requirement received from the FDA also impacts on Acambis' existing cost-plus MVA contractual activities, resulting in certain activities previously anticipated for 2006 continuing into 2007. With this change in the timing of activities and, therefore, revenues, it is expected that "predictable" revenues overall will be marginally lower than the guidance for 2006 of GBP20-25m previously provided. -ends- Enquiries: Acambis plc Gordon Cameron, Chief Executive Officer David Lawrence, Chief Financial Officer Lyndsay Wright, VP, Communications and IR Tel: +44 (0 1223 275 300 Financial Dynamics David Yates/Anna Keeble Tel: +44 (0) 20 7831 3113 About Acambis Acambis is a leading developer of vaccines to prevent and treat infectious diseases. Recognised internationally as the leading producer of smallpox vaccines, Acambis is developing an investigational smallpox vaccine, ACAM2000, and is manufacturing emergency-use stockpiles of this investigational vaccine for the US Government and other governments around the world. It is also developing an attenuated smallpox vaccine, MVA3000, under contracts with the US National Institutes of Health. Acambis' US-based subsidiary Berna Products Corporation markets Vivotif(R), the world's only licensed oral typhoid vaccine, in North America. Acambis' investigational vaccine against Japanese encephalitis, ChimeriVax-JE, is undergoing Phase 3 clinical testing. It also has the most advanced investigational vaccine against the West Nile virus, which has spread to 48 US States in the last seven years, and a vaccine against Clostridium difficile bacteria, a leading cause of hospital-acquired infections. Acambis is based in Cambridge, UK and Cambridge, Massachusetts, US. Its primary listing is on the London Stock Exchange (ACM) and its shares are listed in the form of American Depositary Receipts on NASDAQ (ACAM). More information is available at www.acambis.com. "Safe Harbor" statement under the Private Securities Litigation Reform Act of 1995: The statements in this news release that are not historical facts are forward-looking statements that involve risks and uncertainties, including the timing and results of clinical trials, product development, manufacturing and commercialisation risks, the risks of satisfying the regulatory approval process in a timely manner, the need for and the availability of additional capital. For a discussion of these and other risks and uncertainties see "Risk management" in the Company's 2005 Annual Report and "Risk factors" in its Form 20-F, in addition to those detailed on the Company's website and in the Company's filings made with the Securities and Exchange Commission from time to time. These forward-looking statements are based on estimates and assumptions made by the management of Acambis and are believed to be reasonable, though are inherently uncertain and difficult to predict. Actual results or experience could differ materially from the forward-looking statements. SIGNATURE Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant Peptide Therapeutics Group has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized. Date: 26 July 2006 ACAMBIS PLC By: /s/ Lyndsay Wright Name: Lyndsay Wright Title: VP, Communications and IR.