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U.S. Discusses Adding Avian Strain to Influenza Vaccine
posted by admin on 05/05/06
Move Would Provide Some Viral Protection Against an Outbreak
SINGAPORE -- U.S. public-health officials are considering an unorthodox use of a familiar tool -- the seasonal-flu shot -- as a hedge against a possible pandemic outbreak of avian influenza in humans, according to two experts attending a bird-flu meeting here.
The idea, still only in the discussion phase, would be to add to the existing flu vaccine, already made from several strains of seasonal influenza, protection against the strain of avian influenza that scientists think is likeliest to develop into one that could cause a world-wide outbreak among people.
A shift in the approach to vaccinating people against bird flu would have to jump many hurdles before becoming a reality. For starters, there isn't a stand-alone bird-flu vaccine approved for use, let alone one that might effectively combine different strains of the virus. And any vaccine infusing elements of the bird-flu virus into the seasonal-flu shot would probably require the approval of the U.S. Advisory Committee on Immunization Practices, a group of 15 experts that counsels the Centers for Disease Control and Prevention in Atlanta. It would likely have to be approved by multiple U.S. government agencies after extensive testing.
Rather than wait until any pandemic strain appears, then rush to manufacture a targeted vaccine based on that strain, the object would be to give millions of Americans a tincture of exposure over a period of years. If a bird-flu pandemic then occurred, the thinking is, people would already have a degree of immunity.
James Campbell, an assistant professor of pediatrics at the University of Maryland School of Medicine and one of the main researchers on the clinical trials of the bird-flu vaccine in the U.S., says decision makers are considering the options. "People are serious about testing the combination" vaccine, says Dr. Campbell, one of the attendees at the Singapore meeting organized by the British medical journal the Lancet.
To cause a pandemic, the bird-flu virus would need to mutate to pass easily among people. Current strains can pass from birds to humans, with difficulty, but there is little evidence of human-to-human transmission. Vaccination with a current virus, however, could offer at least some protection until a better vaccine, based on a pandemic strain itself, could be produced. That process would take months -- starting from the isolation of the pandemic strain -- during which millions of lives could be lost, according to some scientists.
Critics of using a current virus say it would repeat the ill-fated attempt by the U.S. government in the 1970s to vaccinate every American against swine flu. That feared outbreak never materialized, but the vaccine killed a number of people and was linked with the development of a rare neurological syndrome.
Even though the bird-flu vaccine currently being developed appears safe so far, those trials involve hundreds of people, not the millions who could potentially receive the combined vaccine. In such a massive administration of the vaccine, side effects that weren't observed in the small study could crop up.
"There's a lot of ferment about this issue," says David Bell, senior adviser for influenza at the division of global migration and quarantine at the CDC. "The previous school of thought was that we had to wait until human-to-human transmission starts, but now there's a sizable debate about that." There was no immediate comment from the CDC.
Meanwhile, Roche Holding AG, maker of Tamiflu, the main antiviral drug used to help fight the disease in people who have contracted it, agreed to take back the drug's raw ingredient from countries that purchased it in the past year, according to its head of pandemic-flu prevention. The offer comes after several European countries expressed concerns that the bulk form of the drug would be useless if a pandemic broke out, given logistical challenges.
Write to Nicholas Zamiska at email@example.com
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