New bird flu vaccine not such a sure bet

According to the Food and Drug Administration (FDA) in the U.S., in clinical trials the nation's first bird flu vaccine is not as effective as was initially expected.

It appears that the two-shot course of injections only provides protection to 45 percent of adults and that was of the highest dose of the Sanofi Aventis SA vaccine.

Earlier tests of the vaccine promised to provide a protective immune response in 54 percent of patients, when measured 28 days after getting the second shot, results of which were published in the New England Journal of Medicine published in March 2006.

The latest results have been released by the FDA prior to a meeting this week where a panel of outside experts will review the vaccine.

The vaccine is the first against the H5N1 influenza strain to seek FDA approval and as a rule the FDA follows the advice of its advisory committees.

The FDA says the study which involved 452 people study showed the vaccine against the deadly H5N1 strain of bird-flu is safe, but it remains unclear whether it would be effective.

Usually seasonal flu vaccines protect 75 percent to 90 percent of vaccinated adults younger than 65.

Drug company Sanofi says the newer analysis applied tougher standards to the final data to show the vaccine works, while the earlier study used interim results.

The French company says the study shows the vaccine's benefits outweigh its risks.