Sanofi Pasteur and International Vaccine Institute Partner Against Dengue

LYON, France, February 21, 2011 - Sanofi Pasteur, the vaccines division of sanofi-aventis Group
(EURONEXT: SAN and NYSE: SNY), announced today that it is partnering with the
International Vaccine Institute (IVI) to support the recently launched Dengue
Vaccine Initiative (DVI). Sanofi Pasteur and the IVI will aim to raise
awareness and to work to move dengue vaccination higher on the global health
agenda.

Currently, there is no specific treatment available for dengue
fever, which is a threat to nearly half of the world's population and a
public health priority in many countries of Latin America and Asia where
epidemics occur. Of the estimated 220 million people infected annually, two
million-mostly children-develop dengue hemorrhagic fever (DHF), a severe form
of the disease[1]. DHF is a leading cause of hospitalization, placing
tremendous pressure on strained medical resources and having a heavy economic
and societal impact.

"Each year, an estimated two million people with dengue
hemorrhagic fever require hospitalization representing a significant burden
on the fragile healthcare systems of developing and endemic nations," said
Dr. Ragnar Norrby, Chairman of the Board of Trustees of IVI. "With a dengue
vaccine on the short term horizon, this collaboration will focus on
accelerating its adoption and introduction and on making it accessible to
those at highest risk of dengue."

The International Vaccine Institute (IVI) announced the launch
of the DVI on February 10, in collaboration with the Sabin Vaccine Institute,
the Johns Hopkins University, and the World Health Organization, to support
development of vaccines to control dengue fever.

"The fight against dengue requires a strong global commitment
from all public health partners. The first dengue vaccine is now in the final
stages of development. The IVI will be a key player in facilitating
discussions among policy makers, with the objective of ensuring that once
licensed the vaccine will be made available to those populations that need it
most in a timely manner," stated Olivier Charmeil, Senior Vice President,
sanofi-aventis, Vaccines.

About International Vaccine Institute

The International Vaccine Institute is an international
organization devoted exclusively to developing and introducing new and
improved vaccines for the world's poorest people, especially children in
developing countries. The IVI conducts research in 30 countries in Asia,
Africa, and Central and South America on vaccines against diarrheal
infections, bacterial meningitis and pneumonia, Japanese encephalitis, and
dengue fever, and develops new and improved vaccines, delivery routes and
adjuvants at its headquarters in Seoul, Korea.

About Dengue Vaccine Initiative

The Dengue Vaccine Initiative (DVI) was established in 2010 to
build on the work of the Pediatric Dengue Vaccine Initiative and to further
awareness of the need to support the development and use of dengue vaccines.
The goal of the DVI is to accelerate the introduction of safe and broadly
protective vaccines into the national immunization programs of endemic and
developing countries. DVI works with scientists, vaccine experts and policy
makers from concept to implementation, promoting the development of dengue
vaccines while also advocating with governments worldwide to ensure the swift
adoption and distribution of a vaccine to those most in need.

Sanofi Pasteur's global dengue vaccine clinical study program

Sanofi Pasteur's candidate dengue vaccine-which targets all
four virus serotypes- is in Phase 3 clinical study. Phase 3 studies are the
ultimate steps in the clinical development of a vaccine before it is
submitted to regulatory authorities for evaluation for market authorization.
Sanofi Pasteur candidate dengue vaccine has been evaluated in clinical
studies (Phase 1, 2) in adults and children in the U.S., Asia and Latin
America. Overall, a balanced immune response against all four serotypes was
observed after three doses of the vaccine. The vaccine is well tolerated with
a similar safety profile after each dose.[2]

Clinical studies in adults and children are ongoing in Mexico,
Colombia, Honduras, Puerto Rico, Peru, the Philippines, Vietnam, Singapore,
Australia, and Thailand.

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). For more information, please visit:
www.sanofi-aventis.com

Sanofi Pasteur, the vaccines division of sanofi-aventis Group,
provides more than 1 billion doses of vaccine each year, 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. For more
information, please visit: www.sanofipasteur.com or
www.sanofipasteur.us

Forward Looking Statements

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defined in the Private Securities Litigation Reform Act of 1995, as amended.
Forward-looking statements are statements that are not historical facts.
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therapeutic alternatives, the Group's ability to benefit from external growth
opportunities as well as 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, 2009. Other than as required by applicable law, sanofi-aventis
does not undertake any obligation to update or revise any forward-looking
information or statements.

[1] PDVI Newsletter No. 7, April 2010 accessible at
www.pdvi.org/PDFs/newsletters/PDVInewsletter7.pdf

[2] Saville et al,
Clinical development of a tetravalent dengue vaccine for endemic areas, ICID
Miami, March 2010; Lang et al, Toward a tetravalent dengue vaccine in Brazil,
Tropical Medicine meeting, Iguacu Falls, March 2010

www.sanofipasteur.com

Contacts, Global Media Relations, Pascal Barollier, T. +33-(0)4-37-37-50-38, pascal.barollier at sanofipasteur.com www.sanofipasteur.com