Research Update

RNS Number:5464I
Acambis PLC
11 March 2003

Smallpox vaccine ACAM2000 completes Phase I trial

Cambridge, UK and Cambridge, Massachusetts - 11 March 2003 - Acambis plc ("
Acambis") (LSE: ACM, NASDAQ: ACAM) announces that it has completed a Phase I
trial of its smallpox vaccine, ACAM2000.

The trial assessed the safety, tolerability and immunogenicity of ACAM2000, in
adult subjects who had not previously been inoculated against smallpox. All 100
subjects in the open-label trial were vaccinated with ACAM2000.

The currently accepted indication of protective immunogenicity in the case of
smallpox vaccination is the development of a pock-mark on the skin, known as a "
take". This "take" was the primary endpoint of the trial and was seen in 99% of
the subjects. A secondary endpoint was the development of a neutralising
antibody response, which occurred in 96% of subjects. No vaccine-associated
serious adverse events were observed.

Under Acambis' accelerated development programme, Phase II trials of ACAM2000
are underway and further results are expected shortly. It is anticipated that
Phase III trials of ACAM2000 will begin later this year.


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Enquiries:

Acambis plc
Dr John Brown, Chief Executive Officer                        Today: [phone]
Lyndsay Wright, Director of Communications                    Thereafter: [phone]
Gordon Cameron, Chief Financial Officer                       Today: [phone]
                                                              Thereafter: [phone]
Financial Dynamics
David Yates/Jonathan Birt                                     Tel: [phone]

MacDougall BioCommunications
Doug MacDougall/Kari Lampka                                   Tel: [phone]



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.

Acambis' smallpox vaccine

Acambis' new smallpox vaccine is based on the same vaccinia virus strain, the
New York City Board of Health strain, that was licensed in the US and used for
routine immunization against smallpox prior to the global eradication of
smallpox in the 1970s. Compared with the previously licensed, first-generation
vaccine, Dryvax(R), improvements have been made both in the development of this
vaccine and the methods by which it is manufactured.

Smallpox vaccination

Vaccinia (cowpox) vaccines have been used to control smallpox for more than 200
years, ever since Dr Edward Jenner's first experiments in 1796. Immunity
develops rapidly following vaccination, generally being protective even in
people already exposed to smallpox and incubating the virus but not yet
clinically ill.  In addition to its ability to protect those exposed to
smallpox, the vaccine can be used to "contain" an outbreak of smallpox, which is
only transmitted person-to-person, in much the same way as a fire-break is used
to prevent the spread of a forest fire.  By immunizing people in the proximity
of a confirmed case of smallpox, the spread of infection can be inhibited.
Vaccinia is delivered by pricking the skin with a special (bifurcated) needle.

"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 and other product development 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.


                      This information is provided by RNS
            The company news service from the London Stock Exchange
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