Harry Greenberg, MD, professor of microbiology and immunology at Stanford University School of Medicine, will present an overview of the hurdles encountered in the development of a live vaccine and the lessons that might apply to development of other important vaccines at a Feb. 13 presentation called "Live Intranasal Influenza Vaccine: A New Era Begins." His talk at the American Association for the Advancement of Science annual meeting is part of a two-day seminar called "Vaccines in the 21st Century."
Greenberg, who was involved in the pre-licensing phases of FluMist while on a leave of absence from Stanford, is also co-director of a large study at Stanford comparing the live attenuated vaccine delivered in the nose against its injected, inactivated counterpart. Researchers hope to observe differences in how the immune system reacts to the two routes of administration. He will discuss this work as well as his overall impression about the process of vaccine development.
"First, the time it takes to develop a vaccine, especially a live attenuated vaccine, can be extremely long," he said. The first description of what became the FluMist vaccine initially was published in 1967, he noted.
When such a long development period is involved, Greenberg noted, evaluation criteria can change. In the case of FluMist, the regulatory agencies increased the number of people it considered sufficient to demonstrate the product's safety after the vaccine was already in late stages of development, prolonging the process.
Because of its genetics, Greenberg said, the flu virus has the ability to outsmart the host immune system, which makes it a moving target for vaccine development. He explained that influenza has a highly efficient mechanism of mutating that allows it to re-infect people and cause severe acute respiratory illness annually, especially in young children and the elderly. It can be an extremely virulent pathogen that could be a target for misuse as an instrument of bioterrorism.
In fact, the vaccine study was funded by a National Institutes of Health bioterrorism grant.
"Understanding respiratory tract immunity has great relevance for biodefense in that the general mechanisms involved can be applied to other pathogens," Greenberg said. But he thinks a lot more is to be learned from this study beyond improving our ability to deal with the bioterrorism threat. "We hope to learn how best to enhance immunity in the respiratory tract for all pathogens."
With the first season of clinical testing for the grant completed, Greenberg and his colleagues are now testing the specimens they have gathered. He said that this analysis may provide intriguing insights into how the two vaccines might work in different ways.
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