Washington, D.C. Good thing that avian flu thing hasn't blown up like we feared.
The nation's first vaccine against bird flu is even less effective than previously thought, according to Food and Drug Administration documents released Monday.
In clinical trials, the two-shot series appears to provide protection to just 45 percent of adults who received the highest dose of the Sanofi Aventis SA vaccine.
An earlier, interim analysis of the same study of the vaccine suggested it sparked a protective immune response in 54 percent of patients, when measured 28 days after getting the second shot. The New England Journal of Medicine published those results in March 2006.
The FDA said the 452-person study showed the vaccine against the deadly bird-flu strain called H5N1 is safe, but it remained unclear whether it would be effective.