Acambis Is First Company To Test A West Nile Virus Vaccine In Older Adults

Acambis plc (Acambis) (LSE: ACM) announces that
clinical testing of its investigational West Nile virus vaccine,
ChimeriVax(TM)-West Nile, is underway in older adults, those most in need
of protection against West Nile virus infection. Acambis' ChimeriVax-West
Nile is the most advanced West Nile virus vaccine in development and the
first to be tested in older adults.


According to the Centers for Disease Control and Prevention, people
over the age of 50 are more likely to develop serious symptoms from West
Nile virus infection; however, individuals of all ages living in areas
where West Nile virus has been identified are at risk. West Nile virus
continues to be a high-profile problem in the US, causing 4,256 cases and
165 deaths in 2006. This is a more than 41% increase in the number of cases
and 38% increase in deaths compared with 2005.



Acambis' Chief Executive Officer Gordon Cameron commented: "The
significant increase in the number of cases and deaths from West Nile virus
last year reinforces the need for a protective human vaccine. Acambis is
the leader in developing a West Nile virus vaccine and we've taken another
important step by testing ChimerVax-West Nile in older adults, the group
most at risk of severe disease from West Nile virus infection."



The trial is designed to evaluate the safety, tolerability and
immunogenicity of ChimeriVax-West Nile in older adults and is being
conducted in the US. The randomised, double-blind, placebo-controlled study
is the second part of a Phase 2 trial evaluating the vaccine.



Previously, Acambis announced encouraging results from the first part
of the Phase 2 trial, which involved younger adults aged 18-40 years. Over
97% of subjects who received a single dose of ChimeriVax-West Nile
developed neutralising antibodies above the predefined cut-off level 28
days after vaccination. The majority of adverse events were mild in nature.



ChimeriVax-West Nile is being developed to provide a safe, single-dose
West Nile virus vaccine for at-risk individuals. There is currently no
human vaccine against this disease so efforts to reduce the incidence of
infection revolve around preventive measures to protect against mosquito
bites, the cause of nearly all human infections of the virus.



While the majority of West Nile infections are mild and asymptomatic,
approximately 20% of those infected will develop symptoms such as fever,
headache, body aches and swollen glands. The more severe West Nile
encephalitis is estimated to occur in one out of every 150 infections.
Symptoms include high fever, neck stiffness, stupor, convulsions, coma and
sometimes paralysis. Death can occur in the most severe cases when the
virus crosses the blood-brain barrier, leading to encephalitis or
inflammation of the brain.
















Since the West Nile virus emerged in the US in 1999, there have been
almost 24,000 cases and 946 deaths.



About ChimeriVax-West Nile



- ChimeriVax-West Nile is being developed to provide a safe,
single-dose West Nile virus vaccine for those at risk from the virus.




- Development of Acambis' investigational vaccine, ChimeriVax-West
Nile, was supported by a $3m grant from the US National Institutes of
Health.



- It is a live, attenuated, injectable vaccine and was developed using
Acambis' proprietary ChimeriVax(TM) technology, which was developed in
association with St Louis University.



- The level of immune response required for protection against West
Nile virus is yet to be determined.



About Acambis



Acambis is a leading biotechnology company targeting infectious
diseases with novel vaccines. Acambis' development-stage pipeline includes
vaccines that could either offer improvements over existing products or
target unmet medical needs. As well as ChimeriVax-JE, Acambis' proprietary
ChimeriVax technology has also been used to develop ChimeriVax-West Nile,
which is undergoing Phase 2 clinical testing, making it the most advanced
investigational vaccine against the West Nile virus. Acambis also has the
only vaccine in development against Clostridium difficile bacteria, a
leading cause of hospital-acquired infections. 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.



Acambis is based in Cambridge, UK and Cambridge, Massachusetts, US, and
is listed on the London Stock Exchange (ACM). More information is available
at acambis/.



"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.


Acambis plc

acambis/