Chiron Updates Delivery Expectations for U.S. Government H5N1 Vaccine Stockpile Contract

Chiron is producing this stockpile at its facility in Liverpool,England, and expects to complete approximately 70 percent of the orderbefore turning operations to annual production of FLUVIRIN(R)influenza virus vaccine in March. Chiron expects to recognize therevenue for the completed doses upon fulfillment of the contract.Chiron expects to resume work on fulfilling the contract following theconclusion of the FLUVIRIN vaccine campaign in the fall of 2006.

As part of its avian influenza vaccine strategy, Chiron expectsthat it can manufacture avian influenza vaccines during thetraditional break between seasonal influenza vaccine campaigns,finishing these activities in time for the seasonal influenza vaccineproduction to avoid interruption of the normal manufacturing cycle.

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.

About Chiron Vaccines

Chiron Vaccines, the world's fifth-largest vaccines business, isheadquartered in Oxford, United Kingdom, and has facilities locatedthroughout Europe, the United States and Asia. Chiron Vaccines is theworld's second-largest manufacturer of flu vaccines and has importantmeningococcal, pediatric and travel vaccine franchises. The company'sportfolio of products includes vaccines for influenza, meningococcusC, rabies, tick-borne encephalitis, Haemophilus influenzae B (Hib),polio, mumps, measles and rubella (MMR) and diphtheria, tetanus andpertussis (whooping cough).

This news release contains forward-looking statements, includingstatements regarding development and manufacturing of pandemicinfluenza vaccines, revenue from stockpiling programs, resumption ofproduction of stockpile H5N1 bulk vaccine for the United States in thefall of 2006, and completion of the FLUVIRIN campaign by the fall of2006 which involve risks and uncertainties and are subject to change.A discussion of the company's operations and financial condition,including factors that may affect its business and future prospectsthat could cause actual results and developments to differ materiallyfrom those expressed or implied by these forward-looking statements,is contained in documents the company has filed with the SEC,including the Form 10-K for the year ended December 31, 2004, and theForm 10-Q for the quarter ended September 30, 2005, and will becontained in all subsequent periodic filings made with the SEC. Thesedocuments identify important factors that could cause the company'sactual performance to differ from current expectations, including,among others, litigation and investigations relating to influenzavaccines, the outcome of clinical trials, regulatory review andapprovals, manufacturing capabilities and issues, intellectualproperty protections and defenses, litigation, stock-price andinterest-rate volatility, and marketing effectiveness. In particular,there can be no assurance that additional issues with respect toinfluenza vaccines or Chiron's manufacturing generally will not arisein the future, or that Chiron will be able to timely complete theproduction of FLUVIRIN vaccine for the 2006-2007 influenza season,successfully develop, manufacture and receive approval to market newproducts (including H5N1 and other pandemic influenza vaccines), orachieve market acceptance for such new products. The company may faceadditional competition in the influenza market in the future andchallenges in distribution arrangements as a result of vaccinedevelopments.

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

(1) The stockpile vaccine is for government supply and is notapproved for general sale.

NOTE: FLUVIRIN is a registered trademark of Chiron.