Chiron Announces Change in Status of SEC Inquiry

    Business Editors/Health/Medical Writers
    BIOWIRE2K

    EMERYVILLE, Calif.--(BUSINESS WIRE)--Feb. 11, 2005--Chiron Corporation (NASDAQ:CHIR) announced today that the U.S. Securities and Exchange Commission (SEC) has issued a formal order of investigation with respect to potential violations of federal securities laws. The previously announced informal inquiry began following the suspension by the UK Medicines and Healthcare products Regulatory Agency (MHRA) of Chiron's license to manufacture FLUVIRIN(R) influenza virus vaccine. Chiron is continuing to cooperate with the SEC's ongoing investigation.
    Chiron does not undertake an obligation to update the information in this release.

    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. For more information, please visit www.chiron.com.

    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 influenza vaccines and has important meningitis, pediatric and travel vaccine franchises. Chiron Vaccines is the leading vaccine manufacturer in the United Kingdom, Germany and Italy. The company's portfolio of products includes vaccines for influenza, meningitis C, rabies, tick-borne encephalitis, yellow fever, haemophilus influenzae B (Hib), polio, mumps, measles and rubella (MMR) and diphtheria, tetanus and pertussis (whooping cough).

    NOTE: FLUVIRIN is a trademark of Chiron Corporation.

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CONTACT: Chiron Corporate Communications & Investor Relations Media, 510-923-6500 Investors, 510-923-2300

KEYWORD: CALIFORNIA UNITED KINGDOM INTERNATIONAL EUROPE INDUSTRY KEYWORD: PHARMACEUTICAL MEDICAL BIOTECHNOLOGY SOURCE: Chiron Corporation

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