Chiron Delivers FLUVIRIN(R) Influenza Virus Vaccine to U.S. Customers; First Shipments Mark Beginning of 2005-2006 FLUVIRIN Supply

Chiron has received all necessary approvals from the U.S. Food andDrug Administration (FDA) and the UK Medicines and Healthcare productsRegulatory Agency (MHRA) to start supplying FLUVIRIN vaccine to theU.S. market. Continued shipments of FLUVIRIN vaccine will undergocorresponding internal release procedures and standard FDA influenzavaccine lot release procedures.

"The efforts and commitments of many have made it possible forChiron to restore the supply of FLUVIRIN vaccine in just one year,"said Howard Pien, chief executive officer of Chiron. "We are gratefulto the government agencies for the expertise they shared as we workedto remediate, and we are proud of our employees for the dedication andperseverance they have shown through both remediation and production.When the MHRA suspended our license a year ago, we set out toimplement a systemic, holistic remediation plan, with the goal ofcoming back within one season and sustaining our supply for thefuture. In this process, we received close oversight from both theMHRA and the FDA, including seven GMP (good manufacturing practices)inspections. Thanks to these efforts, we are again positioned to helpmeet the needs of patients, healthcare providers and customers.Successfully achieving license reinstatement and providing FLUVIRINvaccine to the United States will reestablish Chiron as a trustedsupplier of influenza vaccine."

Chiron has not updated its guidance on total FLUVIRIN vaccinedoses or 2005 financial results since its second-quarter earningsreport on July 27, 2005. The company now expects that the total numberof FLUVIRIN vaccine doses it will produce for the 2005-2006 influenzaseason will be below its previously stated range, due to productiondelays related to remediation as well as lower production outputassociated with adaptation to new processes and procedures implementedin remediation. Accordingly, Chiron expects that its financial resultsfor 2005 will be below its previously stated guidance. Chiron expectsto have more information on FLUVIRIN vaccine production totals andfinancial guidance in the weeks ahead.

"This year, Chiron devoted more than half of the normal productionseason to the implementation of our remediation plan. We are delightedto be back, and we look forward to contributing meaningfully to theinfluenza vaccine supply this year," said Mr. Pien. "Chiron recognizesthe value of influenza vaccines and their important role in publichealth, not just for the annual flu season but also as the foundationfor pandemic preparedness. We are pleased to be able to reiterate ourmission to contribute to protecting people against influenza and willstrive to provide innovations that could help to deal with the threatof pandemic."

Influenza vaccination is the most effective way to preventinfluenza.(1) Although the influenza season can begin earlier, itusually starts in December, peaks in January or February, andcontinues through March. According to the U.S. Centers for DiseaseControl and Prevention (CDC), October and November are the primarymonths for vaccination, and vaccination in December or later isrecommended for those who are not vaccinated earlier. Influenzavaccination not only decreases the risk of illness for the vaccinerecipient but also helps prevent the spread of the influenza virusand limits its role in the potential development of life-threateningcomplications.(2)

"By getting vaccinated against flu each fall, you can help protectyourself, your family, and everyone you interact with from the threatof influenza and the associated lost productivity, suffering andmortality," said William Schaffner, M.D., professor and chairman ofthe Department of Preventive Medicine at Vanderbilt University Schoolof Medicine and member of the board of directors of the NationalFoundation for Infectious Diseases. "Everyone -- and especiallyhealthcare workers, whose work environments put them at the epicenterof flu transmission -- wants to avoid getting the flu themselves and,even worse, passing it along to those who are more vulnerable.

"From a public health perspective, every flu season is a newopportunity to improve vaccination rates," said Dr. Schaffner. "Beyondthe immediate impact of reducing the burden of influenza, increaseddemand for this valuable product drives manufacturers to increasesupply. Every manufacturer's contribution to the nation's vaccinesinfrastructure makes our country better prepared to deliver a robustsupply of this essential tool, both for the prevention of annualinfluenza and a potential pandemic."

Under current CDC recommendations, people with the highest risk ofserious complications from influenza receive priority for flu shotsuntil October 24, 2005. After that date, all people ages 6 months andolder will be eligible to receive flu shots. The priority groupsinclude people ages 65 years and over; residents of long-term carefacilities; people ages 2 to 64 years old with certain chronic medicalconditions; children ages 6 to 23 months old; pregnant women;healthcare professionals who provide direct patient care; andhousehold contacts and caregivers of children younger than 6 months ofage. FLUVIRIN vaccine is not indicated for children younger than 4years of age.

In an average year in the United States, influenza causes morethan 200,000 hospitalizations and kills approximately 36,000 people,primarily in the over-65 population.(3) Together, influenza andpneumonia are the seventh leading cause of death in the country,killing more people than any other infectious diseases. The annualdirect medical costs of influenza are estimated at $3 billion to $5billion. Total direct and indirect costs, including lost work days, ofa severe flu epidemic are estimated at $12 billion to $14 billion.(4)

About Influenza and Influenza Vaccines

Influenza, a contagious disease caused by the influenza virus,affects the respiratory tract, often resulting in cough, sore throat,runny or stuffy nose, as well as fever (usually high), headache,extreme tiredness and muscle aches. It can also lead to complicationssuch as bacterial pneumonia, dehydration and worsening of chronicmedical conditions, such as congestive heart failure, asthma ordiabetes. Children may get sinus problems and ear infections.

Influenza vaccination provides protection from influenza withinabout two weeks of administration. An annual vaccine closely "matched"to the circulating strains of influenza protects about 70 to 90percent of healthy adults who are vaccinated from contractinginfluenza, and vaccinated people who do contract influenza generallydevelop milder cases than those who have not received the vaccine.Among elderly nursing home residents, the flu shot can be 80 percenteffective in preventing death from the flu.(5)

Influenza vaccines are updated each year to address changes in theviruses, and "flu shots" are made with inactivated (killed) influenzastrains (the nasal vaccine is made with live attenuated influenzastrains). The 2005-2006 influenza vaccine contains A/California/7/2004(H3N2)-like, A/New Caledonia/20/99 (H1N1)-like andB/Shanghai/361/2002-like influenza virus antigens. People who areseverely allergic to eggs, who have had a severe reaction to aninfluenza vaccination in the past, or who have previously developedGuillain-Barre syndrome in the six weeks after receiving an influenzavaccination should consult their doctors before receiving influenzavaccination.

Important Safety Information for FLUVIRIN(R) Influenza VirusVaccine

The most common side effect of vaccination with FLUVIRIN vaccineis soreness at the injection site. Less common side effects includefever, malaise, myalgia and allergic reactions. FLUVIRIN vaccineshould not be administered to anyone with a history ofhypersensitivity to any component of the vaccine, including eggs, eggproducts or thimerosal. As is the case with most drugs and vaccines,there is a chance that a serious allergic reaction, serious illness oreven death could occur as a result of vaccination with FLUVIRINvaccine. Generally, persons should not be vaccinated during an acutefebrile illness. FLUVIRIN vaccine is not indicated for use in childrenunder the age of 4 years. Persons should consult with theirhealthcare providers if they are pregnant and/or are taking othermedications. FLUVIRIN vaccine may not protect 100 percent ofindividuals who are susceptible to influenza. Before administeringFLUVIRIN vaccine, please see full prescribing information.

(1)CDC, Key Facts About Influenza and the Influenza Vaccine,September 28, 2005, www.cdc.gov/flu/keyfacts.htm

(2)CDC, Morbidity and Mortality Weekly Report, May 28, 2004, 53(RR-06); 1-40

(3)CDC, Morbidity and Mortality Weekly Report, July 29, 2005,54 (RR-08); 1-40

(4)Monto, A.S., Epidemiology and Virology of Influenza Illness,The American Journal of Managed Care, March 2000. S255-S264.

(5)CDC, Morbidity and Mortality Weekly Report, May 28, 2004, 53(RR-06); 1-40

Media Materials

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About Chiron

Chiron delivers innovative and valuable products to protect humanhealth by advancing pioneering science across the landscape ofbiotechnology. The company works to deliver on the limitless promiseof science and make a positive difference in people's lives. For moreinformation, please visit www.chiron.com.

This news release contains forward-looking statements, includingstatements regarding supply of FLUVIRIN(R) influenza virus vaccinethat Chiron expects to deliver and sell in the 2005-2006 influenzaseason, timing of delivery of FLUVIRIN, duration of the flu season,regulatory approvals, improvements to manufacturing facilities,product development initiatives, and product marketing, that involverisks and uncertainties and are subject to change. A discussion of thecompany's operations and financial condition, including factors thatmay affect its business and future prospects that could cause actualresults and developments to differ materially from those expressed orimplied by these forward-looking statements, is contained in documentsthe company has filed with the SEC, including the Form 10-K for theyear ended December 31, 2004, and the Form 10-Q for the quarter endedJune 30, 2005, and will be contained in all subsequent periodicfilings made with the SEC. These documents identify important factorsthat could cause the company's actual performance to differ fromcurrent expectations, including, among others, additional adversedevelopments resulting from the previous suspension of Chiron's UKlicense to manufacture FLUVIRIN vaccine from October 5, 2004, throughMarch 2, 2005, the announcement of such suspension and the litigationand investigations relating to those matters, the outcome of clinicaltrials, regulatory review and approvals, manufacturing capabilities,intellectual property protections, litigation, marketingeffectiveness, and the severity of the 2005-2006 influenza season. Inparticular, there can be no assurance that additional issues withrespect to FLUVIRIN vaccine or Chiron's manufacturing generally willnot arise in the future, or additional doses of FLUVIRIN vaccine willsatisfy Chiron's internal release procedures and/or FDA influenzavaccine lot release procedures. The company may face additionalcompetition in the influenza market in the future and challenges indistribution arrangements as a result of previous vaccinedevelopments. In addition, the company may engage in businessopportunities, the successful completion of which is subject tocertain risks, including approval by Novartis AG, regulatory approvalsand the integration of operations.

Chiron does not undertake an obligation to update theforward-looking information the company is giving today.

NOTE: FLUVIRIN is a registered trademark of Chiron.