CHIRON GETS PANDEMIC INFLUENZA VACCINE CONTRACT WITH U.K.

Chiron Corporation (NASDAQ:CHIR), Emeryville, Calif., has entered into a supply contract with the UK government for pre-pandemic influenza vaccine for a stockpile based on the H5N1 avian influenza virus strain. The stockpile vaccine is for government supply and is not approved for general sale.

Health authorities have identified H5N1 avian influenza as a strain with pandemic potential.

Under the UK contract, Chiron has agreed to supply the British government with H5N1 avian influenza vaccine containing Chiron's MF59 adjuvant. An adjuvant is a substance that is added to a vaccine to boost the body's immune response to the vaccine's active constituent, called the antigen. Delivery of the stockpile remains subject to internal and regulatory release procedures.

The UK stockpile vaccine is based on an inactivated influenza strain similar to the H5N1 avian subtype that has circulated throughout Southeast Asia and more recently in Central Asia and parts of Europe. Chiron will produce vaccine for this stockpile at its manufacturing facilities in Italy. As part of its avian influenza vaccine strategy, Chiron expects that it can manufacture avian influenza vaccines during the traditional break between seasonal influenza vaccine campaigns, finishing these activities in time for the seasonal influenza vaccine production to avoid interruption of the normal manufacturing cycle.

As with other influenza manufacturers participating in stockpiling efforts, Chiron has also submitted a "mock-up" file for pandemic influenza vaccine containing its MF59 adjuvant to the European Medicines Agency (EMEA). The mock-up file lays the groundwork for potentially a more rapid approval of a vaccine once a pandemic occurs. As part of this process, Chiron has submitted to the EMEA information on its regulatory and development work for a pandemic influenza vaccine. Chiron's mock-up file is based on previous avian influenza vaccine clinical studies and will be augmented with an upcoming study of H5N1 vaccine to take place in Italy this year. All of the studies for the mock-up file involve Chiron's MF59 adjuvant.

Assuming the mock-up file gains approval, in the event of a pandemic Chiron could submit a revision to the mock-up file for the relevant pandemic strain. About Chiron Chiron delivers innovative and valuable products to protect human health by advancing pioneering science across the landscape of biotechnology. The company works to deliver on the limitless promise of science and make a positive difference in people's lives.

About Chiron Vaccines

Chiron Vaccines, the world's fifth-largest vaccines business, is headquartered in Oxford, United Kingdom, and has facilities located throughout Europe, the United States and Asia. Chiron Vaccines is the world's second-largest manufacturer of flu vaccines and has important meningococcal, pediatric and travel vaccine franchises. The company's portfolio of products includes vaccines for influenza, meningococcus C, rabies, tick-borne encephalitis, Haemophilus influenzae B (Hib), polio, mumps, measles and rubella (MMR) and diphtheria, tetanus and pertussis (whooping cough).

For more information, visit http://www.chiron.com or call 510/923-6500.