Acambis announces an update to its smallpox vaccine programme

Cambridge, UK and Cambridge, Massachusetts - 27 August 2003 - Acambis plc
("Acambis") (LSE: ACM, NASDAQ: ACAM) can confirm that it has successfully
completed the production, filling and quality control testing of all 155
million doses of ACAM2000 smallpox vaccine required under its principal
contract with the US Centers for Disease Control and Prevention ("CDC"). Of
these doses, over half have been labelled and delivered to the US stockpile.

Over the past few months, a series of discussions have been ongoing between the
CDC and the US Food and Drug Administration ("FDA") regarding a new label
design for the vials of vaccine that have not yet been labelled. The remaining
vials of ACAM2000 vaccine to be labelled with the new design will be released
and delivered to the US stockpile in the coming weeks.

Acambis' methodology of accounting for revenue under this contract is dependent
upon delivery and not just completion of manufacture of the vaccine. Hence, the
revenues relating to delivery of these remaining vials of vaccine that had
previously been expected in the second quarter of 2003 are now expected to
arise in the third and fourth quarters of this year. Acambis is making no
change to its 2003 full-year revenue and profits guidance given at the time of
its first quarter results statement on 8 May 2003.

With publication of its second quarter results statement scheduled for 16
September 2003, Acambis also expects to provide an update on the ACAM2000
clinical trial programme.

                                    -ends-                                     

Enquiries:

Acambis plc

John Brown, Chief Executive Officer
Lyndsay Wright, Director of Communications
Tel: +44 (0) 1223 275 300

Gordon Cameron, Chief Financial Officer
Tel: +1 (617) 761 4200

Financial Dynamics

David Yates/Jonathan Birt
Tel: +44 (0) 20 7831 3113

Notes to editors:

Acambis is a leading developer of vaccines to prevent and treat infectious
diseases. Recognised internationally as the leading producer of smallpox
vaccines, Acambis provides governments around the world with the full portfolio
of related smallpox vaccine products required to protect their citizens against
the threat of smallpox virus being used as a bioterrorist weapon. Acambis is
establishing a travel vaccines franchise, including vaccines against yellow
fever, Japanese encephalitis, dengue fever and typhoid. Acambis also has the
most advanced vaccine in development targeting the West Nile virus, which has
spread to over 40 US States in the last three years.

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
factors" in the Company's Annual Report and Form 20-F for the most recently
ended fiscal year, in addition to those detailed 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.



END