FDA approves GSK's adjuvanted bird flu vaccine for stockpile

A lot has happened since an FDA advisory panel unanimously recommended GlaxoSmithKline's ($GSK) H5N1 vaccine one year ago. Links between the vaccine's adjuvant and narcolepsy have strengthened, and the FDA subsequently delayed approval. Now, though, GSK has received its long-sought FDA approval.

Late last week, the FDA approved the vaccine for preventing H5N1 influenza, commonly known as bird flu. The FDA based the approval on a trial of 4,500 adults in which 91% of people aged 18 to 64 who received a two-dose regimen had an antibody response consistent with protection against the virus. The vaccine was less effective in people aged 65 years and older but still protected more than two-thirds of those who received two shots.

With H5N1 killing three-fifths of people it infects, the FDA viewed the data as sufficiently compelling to add the vaccine to the national stockpile. "This vaccine could be used in the event that the H5N1 avian influenza virus develops the capability to spread efficiently from human to human, resulting in the rapid spread of disease across the globe," FDA Center for Biologics Evaluation and Research Director Dr. Karen Midthun said.

Bigger question marks hang over the safety of the vaccine. The trial found typical adverse events--such as injection site pain, muscle aches and fatigue--but it is the experience of GSK's H1N1 vaccine that has raised concerns. GSK uses its AS03 adjuvant in both vaccines, and data from the 2009-10 European swine flu immunizations linked it to development of narcolepsy. GSK admits that 800 cases of narcolepsy developed following the immunizations, but says there is insufficient evidence to prove the adjuvant is responsible. 

- here's the FDA's release
- check out Reuters' take
- read FiercePharma's coverage

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