LYON, France, September 18 /PRNewswire/ --

- Clinical Study Demonstrates Breakthrough Dose-Sparing Formulation 
That Increases Stockpile Capacities and Expands Potential Production 
Capacities to Billions of Doses in a Pandemic Situation

Sanofi pasteur, the vaccines division of sanofi-aventis Group,
today announced data showing that its new investigational H5N1 pandemic
influenza vaccine containing a proprietary adjuvant achieved a high immune
response at the lowest dose of H5N1 antigen reported to date.

The vaccine containing only 1.9 micrograms of antigen generated a high
level of seroprotective immune response in over 70 percent of the
participants in a clinical trial and, in the same clinical trial, vaccine
containing 3.75 micrograms of antigen generated a high level of 
seroprotective immune response in over 80 percent of the participants.

Once fully developed, this vaccine should give sanofi pasteur
the potential to provide billions of doses in a pandemic situation and
greatly increases its ability to produce vaccines for stockpiling in advance
of a pandemic. This would be a significant achievement for public health and
a breakthrough in research and development of pre-pandemic and pandemic
vaccines that is fully in line with sanofi pasteur's early commitment to
bring answers to the global threat posed by pandemic influenza.

Results are based on analysis of a clinical trial conducted in
Belgium. The trial involved 266 healthy adults, 18 to 40 years of age. The
vaccine tested was produced from inactivated H5N1 virus and contains a new,
proprietary adjuvant aimed at stimulating the immune system to increase the
response to the vaccine. Trial participants received two doses of each
formulation. Four levels of antigen dose were tested, with 1.9 micrograms 
being the lowest dose.

Preliminary data also show good cross-reactivity to a more
recently circulating H5N1 strain. Further assessment of the ability of this
vaccine to provide cross-protection to variants of the H5N1 strains is
ongoing.

Sanofi pasteur has committed, in the event of a pandemic being
declared by the World Health Organization (WHO), to producing the largest
possible number of doses of its most advanced pandemic influenza vaccine in
the shortest possible time. In order to increase its capacity, sanofi pasteur
initiated clinical trials with a novel adjuvant aimed at dramatically
reducing the amount of antigen needed to elicit a protective immune response
to the H5N1 strain currently identified by global health authorities and
experts as a potential source for the next pandemic.

According to the WHO, the next influenza pandemic could result
in 1 million to 2.3 million hospitalizations and 280,000 to 650,000 deaths in
industrialized nations alone. Its impact is expected to be even more
devastating in developing countries.

With production of 170 million doses of influenza vaccine in
2006, sanofi pasteur confirmed its leadership as the world's largest
manufacturer of seasonal influenza vaccine, supplying a large portion of the
estimated global production of about 350 million doses(1). Sanofi pasteur's
Vaxigrip(R) and Fluzone(R) influenza virus vaccines are licensed in over 100
countries.

Pandemic Influenza Overview

Influenza is a disease caused by a highly infectious virus
that spreads easily from person to person, primarily when an infected
individual coughs or sneezes. An influenza pandemic is a global epidemic of
an especially virulent virus, newly infectious for humans, and for which
there is no preexisting immunity. This is why pandemic strains have such
potential to cause severe morbidity and mortality. In an attempt to minimize
the impact of a pandemic, many countries are developing national and
transnational plans against a possible influenza pandemic situation.

Sanofi Pasteur and Pandemic Preparedness

Sanofi pasteur is committed to global pandemic preparedness.
As the world leader in research, development and manufacturing of influenza
vaccines, sanofi pasteur is actively involved in several pandemic
preparedness projects in the U.S. and Europe, with the goal of developing a
vaccine to protect against a pandemic influenza virus. Sanofi pasteur is also
investing in major expansions of its seasonal influenza vaccine production
facilities in the U.S. and France, which could be used to produce pandemic
influenza vaccine if the need arises.

About sanofi-aventis

Sanofi-aventis is one of the world leaders in the
pharmaceutical industry, ranking number one in Europe. Backed by a
world-class R&D organisation, sanofi-aventis is developing leading positions
in seven major therapeutic areas: cardiovascular, thrombosis, oncology,
metabolic diseases, central nervous system, internal medicine and vaccines.
Sanofi-aventis is listed in Paris (EURONEXT: SAN) and in New York (NYSE:
SNY).

Sanofi pasteur, the vaccines division of the sanofi-aventis
Group, provided more than a billion doses of vaccine in 2006, making it
possible to immunize more than 500 million people across the globe. A world
leader in the vaccine industry, sanofi pasteur offers the broadest range of
vaccines protecting against 20 infectious diseases. The Company's heritage,
to create vaccines that protect life, dates back more than a century. Sanofi
pasteur is the largest company entirely dedicated to vaccines. Every day, the
company invests more than EUR1 million in research and development. For more
information, please visit: http://www.sanofipasteur.com or
http://www.sanofipasteur.us

Forward Looking Statements

This press release contains forward-looking statements as
defined in the Private Securities Litigation Reform Act of 1995, as amended.
Forward-looking statements are statements that are not historical facts.
These statements include financial projections and estimates and their
underlying assumptions, statements regarding plans, objectives, intentions
and expectations with respect to future events, operations, products and
services, and statements regarding future performance. Forward-looking
statements are generally identified by the words "expects," "anticipates,"
"believes," "intends," "estimates," "plans" and similar expressions. Although
sanofi-aventis' management believes that the expectations reflected in such
forward-looking statements are reasonable, investors are cautioned that
forward-looking information and statements are subject to various risks and
uncertainties, many of which are difficult to predict and generally beyond
the control of sanofi-aventis, that could cause actual results and
developments to differ materially from those expressed in, or implied or
projected by, the forward-looking information and statements. These risks and
uncertainties include those discussed or identified in the public filings
with the SEC and the AMF made by sanofi-aventis, including those listed under
"Risk Factors" and "Cautionary Statement Regarding Forward-Looking
Statements" in sanofi-aventis' annual report on Form 20-F for the year ended
December 31, 2006. Other than as required by applicable law, sanofi-aventis
does not undertake any obligation to update or revise any forward-looking
information or statements.

For more information please visit http://pandemic.influenza.com

Reference (1): 
http://www.who.int/vaccine_research/diseases/ari/en/print.html

Sanofi Pasteur
    Pascal Barollier
    International Media Relations
    Tel: +33-(0)4-37-37-51-41
    pascal.barollier@sanofipasteur.com 

    Len Lavenda
    U.S. Media Relations
    Tel: +1-570-839-4446
    len.lavenda@sanofipasteur.com