April 14, 2006

Progress toward Avian Flu Virus Vaccine

photo of a vacccine

You've probably heard that avian flu viruses from a class called H5N1 have now infected birds throughout Southeast Asia and are spreading into Central Asia, Africa and Europe. They've infected some people, too. So far, the viruses can't move easily from person to person, but if they learned how it could cause an influenza pandemic. Human immune systems aren't well prepared to fight these types of viruses; of the 190 cases reported to the World Health Organization so far, more than half have been fatal. Results from a new study funded by NIH's National Institute of Allergy and Infectious Diseases (NIAID) show that researchers may be on the path to develop a vaccine to protect people.

The vaccine they tested was made from an H5N1 virus originally isolated in Southeast Asia in 2004. It was manufactured in an "inactivated" form — one altered so it can't infect people — by sanofi pasteur under contract to NIAID.

The research team assigned 451 healthy adults between 18 and 64 years old at random to 5 groups. Each received either a placebo or 1 of 4 different doses of the vaccine. They got 2 shots into their upper arm muscle about a month apart. Their blood was collected and tested to see what amounts of the virus-fighting molecules called antibodies their bodies had made.

The results were published in the March 30 issue of The New England Journal of Medicine. The higher the dose of vaccine, the more antibodies people produced. Of the 99 people in the highest-dose group, about half produced levels of antibody that the researchers predict would neutralize the virus. Almost all the side effects were mild.

Although some hoped that the vaccine might work better than it did, these results are still a step in the right direction, according to NIAID director Anthony S. Fauci. Researchers are now testing several ways to make a more effective H5N1 vaccine, including adding immune boosters known as adjuvants to try to stimulate more effective antibody production.

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