Sanofi Pasteur, the vaccines division of sanofi-aventis Group (EURONEXT: SAN and NYSE: SNY), announces it is ready to support public health efforts to respond to the emergence of the new A(H1N1) influenza strain following the decision made by the World Health Organization (WHO) to raise the pandemic alert level from Phase 5 to Phase 6, the highest level of alert in the WHO global influenza preparedness plan.

“By committing to develop and supply a vaccine against the new influenza A(H1N1) strain,
Sanofi Pasteur supports the fight against pandemic influenza led by the WHO, the Department of
Health and Human Services (HHS) and the Centers for Disease Control and Prevention (CDC) in the
United States, the European Institutions, the French Ministry of Health and other national and
international health authorities around the world”, said Wayne Pisano, President and CEO of
Sanofi Pasteur. “Sanofi Pasteur remains in continuous communication with these health authorities to
help develop a tailored response to local public health needs”.

As the world’s largest supplier of influenza vaccine, Sanofi Pasteur is currently implementing its internal pandemic preparedness plans to ensure its continued ability to fulfill its public health mission to produce the largest number of doses of vaccine in the shortest time frame to face the threat of pandemic influenza while maintaining the production of other life-saving vaccines.

The company received the new A(H1N1) seed virus from WHO International Reference Centers, and
has begun preparation of a working seed to be used for vaccine production. Sanofi Pasteur currently
estimates it will have the first bulk concentrate vaccine within four to six months. This vaccine would
help prevent the spread of the new influenza A (H1N1) virus strain. Its availability would be subject to
regulatory approval.

Sanofi Pasteur received an order from the U.S. Department of Health and Human Services (HHS) on
May 25, 2009 for the supply of an A(H1N1) influenza vaccine.

Sanofi Pasteur’s response to the emergence of a new A(H1N1) influenza strain is to maintain flexibility in its influenza vaccine production. The company will continue to manufacture its seasonal influenza vaccine for the 2009/2010 Northern Hemisphere influenza season as recommended by the WHO. Production of seasonal influenza is still a priority as seasonal influenza is a very serious illness causing 250,000 to 500,000 deaths per year.

Phase 6 is characterized by human-to-human spread of a pandemic influenza virus and community
level outbreaks in at least two WHO regions of the world. Designation of this phase indicates that a
global pandemic is under way, according to the WHO. However, Phase 6 is not an indication of the
severity of the influenza pandemic.

Sanofi Pasteur Influenza Vaccine Production

Sanofi Pasteur operates influenza vaccine production facilities in Swiftwater, Pennsylvania, United
States, and Val de Reuil, France. All Sanofi Pasteur influenza vaccine facilities have been designed
and built to be able to switch from seasonal influenza vaccine production to pandemic influenza vaccine production.

In Swiftwater, Sanofi Pasteur has two licensed influenza production facilities. On May 6, 2009, the FDA licensed Sanofi Pasteur’s new influenza vaccine manufacturing facility in Swiftwater. When operating at full capacity, the new facility will have a capacity of approximately 100 million doses of seasonal influenza vaccine per year. An existing facility in Swiftwater is capable of producing 50 million doses per year and currently is producing vaccine for the 2009/2010 season. In total, the company will have a capacity equivalent to approximately 150 million doses of trivalent seasonal influenza vaccine per year in the United States when both facilities are operating at full capacity. The A(H1N1) production can occur in both Swiftwater facilities.

In Val De Reuil, Sanofi Pasteur is currently producing the trivalent seasonal influenza vaccine for the
2009/2010 season, with the capacity of 120 million doses per year. Sanofi Pasteur’s production facility in Val De Reuil is also capable of producing the new A(H1N1) vaccine.

Sanofi Pasteur produces approximately 40 percent of the influenza vaccines distributed worldwide and
in the United States produced more than 45 percent of the influenza vaccines distributed for the
2008/2009 influenza season. The company also has developed the first and only U.S.-licensed avian
influenza vaccine for humans.

About Sanofi Aventis

Sanofi-aventis, a leading global pharmaceutical company, discovers, develops and distributes
therapeutic solutions to improve the lives of everyone. Sanofi-aventis is listed in Paris (EURONEXT:
SAN) and in New York (NYSE: SNY).

Sanofi Pasteur, the vaccines division of sanofi-aventis Group, provided more than 1.6 billion doses of
vaccine in 2008, 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 EUR 1 million in research and development.

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 sanofiaventis’ 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”
Page 3 of 3 and “Cautionary Statement Regarding Forward-Looking Statements” in sanofi-aventis’ annual report on Form 20- F for the year ended December 31, 2008. Other than as required by applicable law, sanofi-aventis does not undertake any obligation to update or revise any forward-looking information or statements.

Source: Sanofi Pasteur