Bird Flu: Science and Policy

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Chiron Announces Promising Data from Clinical Study of Adjuvanted Avian Influenza Vaccine; Results Confirm Previous Clinical Studies: Chiron's MF59 Adjuvant Significantly Enhances Immune Response
10/28/2005 9:00:00 AM EST

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Chiron Corporation (NASDAQ:CHIR) today announced preliminary promising data from a clinical study of its investigational vaccine against an H9N2 avian influenza strain that has infected a small number of people and may have the potential to cause a human pandemic. The trial was supported by the National Institute of Allergy and Infectious Diseases (NIAID), part of the U.S. National Institutes of Health (NIH).

The 96-patient study explored the safety and immunogenicity of four different doses of the investigational vaccine with and without Chiron's adjuvant MF59. An adjuvant is a substance that is added to a vaccine to boost the body's immune response to the vaccine's antigen. All vaccine formulations containing the adjuvant MF59 proved highly immunogenic, inducing antibody levels believed to confer protection against the influenza strain. The lowest dose contained 3.75 micrograms of antigen per dose, a quarter of the dose used in seasonal influenza vaccines. In marked contrast, the unadjuvanted vaccine induced significantly lower antibody titers and did not reach levels achieved by the adjuvanted vaccine following any of the antigen doses tested, which ranged from 3.75 to 30 micrograms.

"This study builds on the clinical data Chiron has already established with adjuvanted influenza vaccines," said Rino Rappuoli, Ph.D., chief scientific officer of Chiron and head of research for Chiron Vaccines. "With more than 20 million doses of MF59-adjuvanted vaccine distributed outside of the United States for seasonal vaccination, we have built an impressive safety database. In addition, our previous clinical studies of a vaccine designed to protect against H5 avian influenza have demonstrated the potential of our adjuvant to reduce the required dose of antigen and to cross-protect against a range of related viral strains.

"This important collaborative research further advances our understanding of the role innovative adjuvant technology can play in enhancing the immune response to pandemic vaccines, providing the potential for dose-sparing to stretch production capacity," continued Dr. Rappuoli. "Following these successful results, we look forward to clinical studies of an adjuvanted H5N1 vaccine planned for the near future."

"Adjuvants could be an important means of improving the immune response to potential pandemic strains and allow us to stretch production capacity," added Walter A. Orenstein, M.D., professor of medicine of pediatrics and associate director of the Emory Vaccine Center in Atlanta, Georgia.

"Public-private partnerships are an essential part of our preparations for a potential pandemic, and this study clearly demonstrates their value," said Dan Soland, president of Chiron Vaccines. "NIAID has taken the lead in sponsoring clinical trials to determine the optimal characteristics of an effective and safe pandemic vaccine. This trial builds on that knowledge, providing valuable data on the importance of using adjuvants, which may be critical for extending the vaccine supply to reach as many people as possible."

About Pandemic Influenza

Pandemic influenza occurs when a new influenza virus emerges that is easily transmitted among humans and causes serious illness. In this situation, the virus can result in a worldwide outbreak of disease, or pandemic. Pandemic influenza occurred three times in the last century. The 1918 pandemic killed at least 40 million people worldwide, with a mortality rate of approximately 2.5 percent in the United States.

Avian influenza, or "bird flu," does not normally infect humans, but there have been several examples in recent years of transmission to people, leading to fears of a strain with the potential to result in a pandemic. The current outbreak of H5N1 avian influenza in Southeast Asia has resulted in more than 100 human cases, in Cambodia, Indonesia, Thailand and Vietnam, with a mortality rate of approximately 50 percent. Despite the death or destruction of an estimated 150 million birds, the virus is now considered endemic in a number of regions in Southeast Asia.