An experimental vaccine from
to guard against avian flu appears safe, according to a staff report from the Food and Drug Administration.
The report was issued Monday, one day before a committee of outside medical experts was set to review test data for what could be the first vaccine against the dangerous disease. The FDA isn't bound by recommendations from advisory panels, but it usually follows their suggestions.
Clinical testing of Sanofi-Aventis' vaccine revealed "no significant safety signals that would preclude administration of this vaccine to additional persons," the FDA staff report says. The testing also indicates patients build up a better defense vs. the virus if they receive the highest dose rather than lower doses.
FDA staff reports are routinely issued prior to advisory panel meetings; these documents offer questions for panel members to ask drugmakers during hearings.
"The questions to the committee will focus on the adequacy of the data to support" approval of the vaccine, the FDA report says. "If the data are not deemed adequate, the committee will be asked what additional data would be needed to support approval."
Even if the data are adequate, the advisory committee will be asked what post-marketing studies would be needed "to assess the benefit and risk" of the vaccine, the staff report says.
Potential for Widespread Demand
Other drug companies, including
, are pursuing vaccines to protect people against pandemics -- widespread outbreaks of diseases for which people have little or no immunity. The best example of a flu pandemic occurred in 1918 and 1919, during which time about 50 million people were killed worldwide.
Recent research suggests that the 1918-19 flu likely resulted "from a series of multiple genetic mutations in multiple genes" in a virus that started out as a bird flu, the FDA says. "These mutations appear to have allowed the virus to adapt to and spread among humans."
Mutation and adaptation worry public health officials about the flu virus called H5N1. The FDA says there have been 270 cases in 10 countries of people contracting bird flu -- with a death rate of 60%. The first case of the H5N1 bird flu infecting a human was in Hong Kong in 1997.
Compounding the problem of prevention is the fact that public health experts aren't sure how the flu virus might mutate, thus reducing a vaccine's effectiveness. Developing vaccines for a pandemic that hasn't happened yet is filled with challenges such as producing enough product for governments to stockpile, creating a vaccine that remains stable for a long period of time, and planning for mass vaccination campaigns.
Tests of the Sanofi-Aventis vaccine were conducted by the National Institutes of Health, which has awarded contracts to the French company and to other drugmakers to develop a bird flu vaccine. Of the 452 people enrolled in the study at three U.S. medical centers, 405 completed full testing. Some dropped out, and others committed test protocol violations such as missing visits.