Chiron Submits Written Testimony to Government Reform Committee Hearing on Influenza Vaccine Supply; CEO Howard Pien Pledges Company's Commitment to U.S. Influenza Vaccine Market.

EMERYVILLE, Calif. -- Chiron Corporation (Nasdaq:CHIR) today announced that president and chief executive officer Howard Pien has submitted written testimony for today's Government Reform Committee Hearing on "The Nation's Flu Shot Shortage: How it Happened and Where We Go From Here."

"As we have from the beginning of this situation, Chiron intends to be open and transparent with you and Federal authorities regarding our manufacturing situation," Mr. Pien said in his statement. "Going forward, our primary objective is to ensure that we restore our ability as a reliable supplier of influenza vaccine to the United States and become a dependable partner to those who are battling to reduce the burden of influenza."

On October 5, Chiron announced that the UK regulatory body, the Medicines and Healthcare Products Regulatory Agency (MHRA), had temporarily suspended the company's license to manufacture Fluvirin(R) influenza virus vaccine in its Liverpool facility, preventing the company from releasing any of the product during the 2004-2005 influenza season.

Mr. Pien said that the company had taken actions to address the concerns raised by the MHRA in its October 5 letter to Chiron. On October 6, senior management representatives from Chiron Vaccines met with the MHRA and initiated a dialogue to better understand the agency's concerns about the Liverpool facility and how those concerns can be addressed. Mr. Pien said that the company's hope was that the meeting would lead to a remediation plan that would permit the lifting of the suspension if, in the MHRA's view, the plan is successfully implemented.

The testimony also included Mr. Pien's affirmation of Chiron's resolve to take all appropriate actions to discover how the company could improve its operational and managerial procedures, and to implement a program of change to ensure that Chiron can expeditiously regain its license. Specifically, Mr. Pien pointed to:

--Systematically examining Chiron's manufacturing capabilities, including quality control, and processes for managing risk contingencies. Chiron will make the necessary investments to ensure that the company meets the highest standards of GMP.

--Ensuring that, in addition to the routine inspections that Chiron facilities undergo, the company is in frequent contact with regulatory authorities to understand any concerns that may exist and address them proactively.

--Assessing the company's processes for communication with key public health stakeholders to identify any opportunities for enhancement.

The testimony in its entirety can be found at www.chiron.com.

About Chiron

Through its global Blood Testing, Vaccines and BioPharmaceuticals businesses, Chiron Corporation addresses human suffering with more than 50 diverse products to detect, prevent and treat disease worldwide. The company's consistent success has come from its pioneering science, skill in delivering innovations in biotechnology and disciplined business approach. Chiron believes that science has the power to improve people's lives and harnesses that power to transform human health. For more information about Chiron, please visit www.chiron.com.

This news release contains forward-looking statements, including statements regarding the supply of Fluvirin that Chiron expects to deliver to the U.S. market in future influenza seasons, sales growth versus prior periods, product development initiatives, and new product marketing. These forward-looking statements involve risks and uncertainties and are subject to change. No assurances can be given that additional issues with respect to Fluvirin or Chiron's manufacturing generally will not arise in the future or that the MHRA will not further suspend or revoke the license to Chiron's Liverpool facility. Many factors could cause actual results and developments to differ materially from those expressed or implied by these forward-looking statements, including, among others, additional adverse developments resulting from investigations or discussions with or actions taken or required by the MHRA, FDA, U.S. Department of Health and Human Services, or CDC. In addition, a full discussion of the company's operations and financial condition, including factors that may affect its business and future prospects, is contained in documents the company has filed with the SEC, including the form 10-Q for the quarter ended June 30, 2004, and the form 10-K for the year ended December 31, 2003, and will be contained in all subsequent periodic filings made with the SEC. These documents identify other important factors that could cause the company's actual performance to differ from the expectation expressed or implied by these forward-looking statements, including the outcome of clinical trials, regulatory review and approvals, manufacturing and testing capabilities, pricing pressures, intellectual property protections and defenses, litigation, stock-price volatility, and marketing effectiveness. In particular, there can be no assurance that Chiron will timely maintain anticipated levels of profitability, increase sales of existing products, successfully develop and receive approval to market new products, or achieve market acceptance for such new products. In addition, the company may engage in business opportunities, the successful completion of which are subject to certain risks, including shareholder and regulatory approvals and the integration of operations.

Consistent with SEC Regulation FD, we do not undertake an obligation to update the forward-looking information we are giving today.

NOTE: Fluvirin is a trademark of Chiron Corporation.