— The first potential bird flu vaccine for humans to help prevent a widespread outbreak in the US won support from US experts on Tuesday as an interim measure until better versions come along.
The experimental vaccine, made by Sanofi-Aventis, would be the only US-approved vaccine for the H5N1 influenza virus in case of a pandemic if the Food and Drug Administration later approves it.
While no US cases of the virus have been reported, a rising number of outbreaks in birds and humans in other countries have FDA and other federal agencies concerned.
"The timing and severity of the next pandemic we cannot predict. However, the probability that a pandemic will occur has increased," Norman Baylor, head of the FDA's vaccine office, told the panel of outside experts.
While several other manufacturers, including Novartis AG and GlaxoSmithKline Plc, are also developing H5N1 vaccines, Sanofi is the first to seek US approval.
The panelists overwhelmingly said Sanofi's version was effective and safe enough given that it is the only option right now. Still, limited data from a small study left much unknown. About 45% of the 91 people inoculated with the bird flu version had an immune system response, according to the FDA; 42 patients received a placebo.
"I hope we never have to use it," says panel member Melinda Wharton of the Centers for Disease Control and Prevention.
Robert Webster, a panelist from St Jude Children's Research Hospital in Memphis, Tennessee, US, says the vaccine is "the first very important step ... there's a long way to go".
Still, the panel members say they do not want to leave officials and citizens without options. Approving Sanofi's vaccine would also encourage other drugmakers, some added.
The FDA will weigh their recommendations as it makes its approval decision, but it usually follows the advice of its panels.
Sanofi's vaccine would not be sold commercially. Instead, the federal government could stockpile it in case of a pandemic or for those at higher risk to contract the H5N1 virus. Adults ages 18 to 64 would receive two injections 28 days apart.
At the meeting, Health and Human Services officials said they were seeking 20 million doses to first innoculate critical workers, as well as about another 600 million doses, or enough for all citizens, within six months of an outbreak.
HHS officials have already awarded multimillion dollar grants to Sanofi and other drugmakers for some doses. In a statement, Sanofi said it would work with officials to stockpile the vaccine and was building new facilities to double its manufacturing capacity.
The H5N1 virus so far affects mostly birds, but it has infected humans. Worldwide, 274 people have been infected since 2003, and 167 of them have died, according to the World Health Organization.
Scientists fear the strain could change and spread easily person-to-person, killing tens of millions of people. If it does mutate, it is unclear if vaccines under development now would still work.
While the panel supported Sanofi's vaccine, FDA officials say better vaccines with more robust protection would eventually displace it. "This is in the interim ... to get us through this period," Baylor says. "We're moving into other generations of vaccines."
Glaxo and Novartis are developing such versions using novel adjuvants substances added to vaccines to boost immune system response, while Iomai Corp has a skin patch to boost vaccine impact. Sanofi says it is also working on different dosing and newer technology as well as adjuvants.
FDA staff expressed concern that the immune response among patients to Sanofi's vaccine was not as strong as to its seasonal flu counterpart. Its effect on women, minorities and those who had seasonal flu shots was also unknown, they added.