The Food and Drug Administration on Tuesday approved the first vaccine for humans against avian flu.
The agency endorsed the
vaccine six weeks after a panel of
outside medical experts unanimously recommended that the FDA support it.
The vaccine, which will be administered by two injections one month apart, won't be sold commercially. Instead, it will be sold to the federal government for stockpiling against a potential outbreak of the flu virus called H5N1.
"The threat of an influenza pandemic is, at present, one of the most significant public health issues our nation and world faces," said FDA Commissioner Dr. Andrew von Eschenbach, in prepared remarks. "The approval of this vaccine is an important step forward in our protection against a pandemic."
The H5N1 virus is one version of the influenza A virus commonly found in birds, the FDA says. When bird flu strikes humans, the symptoms are more severe and hit more quickly than symptoms from seasonal influenza. "Pneumonia and multiorgan failure
are commonly seen," the agency says.
Although there haven't been any reported bird flu cases in the U.S., the FDA says almost 300 people worldwide have been infected since 2003 and more than half have died.
"To date, H5N1 influenza has remained primarily an animal disease, but should the virus acquire the ability for sustained transmission among humans, people will have little immunity ... and the potential for an influenza pandemic would have grave consequences for global public health," the agency says.
The FDA review was based on a clinical trial completed in 2005 showing that the Sanofi-Aventis vaccine has an effectiveness rate of 45% when tested on adults between the ages of 18 and 64.
The effectiveness for seasonal flu vaccines ranges in percentages "from the 70s to the 90s," depending on the vulnerability of the population and a vaccine's ability to match with a particular flu strain, Norman Baylor, director of FDA's office of vaccines research and review, said.
Baylor said the Sanofi-Aventis vaccine is the best product available now, even as companies and academic researchers try to develop vaccines that would be more effective and easier to use. "At this point, this is where we are," he remarked during a telephone press conference.
"We can't predict how effective the next generation
of vaccine will be," he said. "Ideally, we would like to see higher efficacy. Baylor said his wish list includes a vaccine that could be administered in a single dose.
The current vaccine has a shelf-life of 18 months. Baylor said he didn't know how much vaccine was being produced or how much would be stockpiled.
One unanswered question is how effective this vaccine will be -- or how effective new vaccines will be -- if the avian flu virus mutates.