New study tackles bird flu protection

(Oct. 13) Washington- A unique study suggests a possible way to kick-start people's protection against bird flu just in case the virus triggers a worldwide outbreak years from now.

If a flu pandemic should begin, it would take several months to tailor a vaccine to the precise strain causing illness and then to make enough vaccine. Worse, people almost certainly would require two doses to protect against a flu strain their bodies had never encountered.

Scientists have long wondered if giving shots in advance might help, a vaccine that would not fully protect but would introduce people's immune systems to a new type of flu. Then, once a pandemic had begun, they would need one booster shot of vaccine tailored to the exact strain, which would cut significantly the time it would take to protect a population.

On Friday, University of Rochester scientists are reporting the first evidence that this so-called "prime-and-boost" method could work.

If the findings hold up, they raise the possibility of giving "priming" shots to doctors, nurses and other first-responders who would be on the front lines of a flu pandemic long before much vaccine was ready. A decision also might be made even to offer such shots to whoever wanted them.

"You'd have people who were prepared as much as possible in advance," said Dr. John Treanor, a Rochester vaccine specialist who led the research. "It is something a lot of people are very, very interested in. It does have some major implications for policy."

The researchers tracked down 37 people who had tested an experimental bird flu vaccine in 1998. At the end of 2005, each got a single booster shot designed to fight a different strain of the H5N1 virus.

H5N1 is thought to have made its first jump from poultry into people in Hong Kong in 1997. The Rochester volunteers got their first inoculations with vaccine made from that Hong Kong strain.

The deadly Asian bird flu has continued evolving as it hop-scotched across the globe, and the booster doses were made from a very different strain that emerged in Vietnam in 2004. The booster recipients were compared with people vaccinated for the first time against the Vietnam strain.

The booster method worked better, Treanor and colleague Dr. Nega Ali Goji will report on Friday at a meeting of the Infectious Diseases Society of America.

More than twice as many of the booster recipients had a protective immune response compared with people given their first-ever doses of H5N1 vaccine. They even seemed a little more protected than those who got the optimal two doses.

The findings are intriguing, said Dr. Anthony Fauci, infectious disease chief at the National Institutes of Health, which paid for the work.

"It really does add some degree of scientific credibility to the issue of priming," Fauci said.

But, he cautioned, much more research is needed before the government would even consider recommending advanced shots for bird flu: "Policy decisions would require considerably more information than we have."

The work reflects what happens every winter with seasonal flu. When small children are first vaccinated against regular flu, they need two doses. After that, one shot a year is enough. Even though the strain that circulates each winter is slightly different, the shot awakens the immune system's memory of influenza just enough.

"Your flu vaccine experience is a constant series of booster doses," Treanor explained.
(from AP)


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