September 12, 2006

Live bird flu virus vaccine more potent than traditional ones

Three experimental vaccines using live but weakened versions of the H5N1 bird flu virus appeared to protect animals from infection, US researchers said on Monday (Sep 11).

Maryland-based MedImmune Inc is engineering a live but weakened virus that is delivered as a nasal spray instead of injected by needle.

MedImmune researchers worked with teams at the National Institutes of Health and the USDA to make a live H5N1 vaccine.

Mice that got a single dose of vaccine, given in a nose spray, all survived normally lethal doses of H5N1, the researchers reported. Mice and ferrets given two doses of vaccine were protected and their bodies also suppressed the virus, the researchers found.

The approach might be the start of a repository of vaccines against various potential strains of pandemic influenza.

Researchers have been working on live, attenuated influenza virus vaccines because they have properties that make them attractive vaccines for flu-prevention.

Unlike typical vaccines, the live vaccine needs only to be given in single doses to stimulate a good immune response, the researchers said.

Such vaccines induce cross-protection, meaning the vaccine protects against other similar strains of the virus. The trait makes it more effective against the flu virus, which mutates often and forces drug manufacturers to come up with a new drug each time it mutates.

If an influenza pandemic were imminent, a vaccine that could stimulate immunity quickly would be needed, said National Institute of Allergy and Infectious Diseases Director Dr Anthony Fauci. Thus, a live virus would be seemingly the right approach to take, he said.