An FDA advisory panel has voted in favor of a vaccine against the highly pathogenic H5N1 avian flu that would be stockpiled and used in case of pandemic.
By twin votes of 14-0, the panel agreed that the immunogenicity and the safety of the vaccine, made in Quebec by GlaxoSmithKline, were enough to meet licensing standards under accelerated approval regulations.
Those rules -- set out in 2007 -- allow rapid approval of a vaccine on the basis of markers that are likely to predict clinical benefit. In the case of this vaccine, dubbed Q-Pan H5N1, the surrogate marker was antibody response measured by a hemagglutination-inhibition (HI) assay.
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Flu experts have been watching the H5N1 avian flu for years, fearing it might mutate in a way that would allow it to spread as easily among humans as it does among domestic and wild fowl.
Currently, the virus only rarely infects humans but when it does, it is highly dangerous. As of Aug. 10, according to the World Health Organization, there have been 608 cases since 2003 -- 359 of which ended in death.
The Q-Pan H5N1 vaccine, developed under contract with the Department of Health and Human Services, consists of a monovalent, inactivated, split A/H5N1 influenza virus antigen and Glaxo's AS03 adjuvant.
In clinical trials, the most common adverse events were injection site pain and swelling, muscle aches, headache, fatigue, joint pain, shivering and sweating, according to briefing documents prepared by FDA staff reviewers.
The rates of those events were increased compared with unadjuvanted H5N1 antigen or saline placebo.
On the other hand, antibody responses to the vaccine were better than for unadjuvanted H5N1 antigen.
The FDA does not have to follow the recommendations of its advisory panels, but it usually does.
"We now look forward to a final decision by the FDA later this year," Bruce Innis, Glaxo's vice-president of vaccine discovery and development, said in a statement.
The U.S. contract with Glaxo called for the company to develop an antigen-sparing vaccine, which would allow more doses to be made with a given amount of antigen.
The Q-Pan H5N1 candidate contains 3.75 mcg of the H5N1 antigen, less than the 90 mcg in an already-okayed vaccine developed by Sanofi Pasteur at its Swiftwater, Pa., plant.
The adjuvant boosts the vaccine's immunogenicity to compensate for the small amount of antigen.