The first potential bird flu vaccine for humans aimed at helping prevent a widespread outbreak in the USA won support from a panel of US experts on 27 February.
The drug would serve as an interim measure until better versions were developed.
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 US Food and Drug Administration later approves it.
While no US cases of H5N1 have been reported, rising numbers of outbreaks in birds and humans in other countries have FDA and other US federal agencies concerned.
Norman Baylor, head of the FDA’s vaccine office, told the panel of outside experts: “The timing and severity of the next pandemic we cannot predict. However, the probability that a pandemic will occur has increased.”
Several other manufacturers, including Novartis and GlaxoSmithKline, are also developing vaccines against H5N1, but Sanofi is the first to seek US approval.
The panel members overwhelmingly said Sanofi’s version was effective and safe enough, given that it was the only option right now. But with results based on limited data from a small study, much remained unknown.
The FDA said 45% of the 91 people inoculated with the bird flu version had an immune system response. Forty-two patients received a placebo.
Dr Robert Webster, a panelist from St Jude Children’s Research Hospital in Memphis, Tennessee, USA, said the vaccine was “the first very important step”, but there was “a long way to go”. Still, the panel members did not want to leave officials and citizens without options – and approving Sanofi’s vaccine would also encourage other manufacturers.
The FDA will weigh up the panel’s recommendations as it makes its decision on approval, but it usually follows the advice of its panels.
Sanofi’s vaccine would not be sold commercially. Instead, the US government could stockpile it in case of a pandemic or for those at relatively higher risk of contracting the virus. Adults aged 18 to 64 would receive two injections 28 days apart.
At the meeting, US Health and Human Services officials said they were seeking 20 million doses for inoculating critical workers, plus 600 million more doses – enough for all citizens – within six months of an outbreak. The HHS has already awarded multimillion-dollar grants to Sanofi and other manufacturers for some doses.
In a statement, Sanofi said it would work with officials to stockpile the vaccine and was building new facilities to double manufacturing capacity.
The H5N1 virus so far affects mostly birds, but it has infected humans. Of the 274 people infected worldwide since 2003, 167 have died, according to the World Health Organization.
Scientists fear the strain could mutate and spread easily from person to person, killing tens of millions. If it does mutate, it is unclear whether vaccines now under development would still work.
FDA officials said better vaccines with more robust protection would eventually displace Sanofi’s product.
Glaxo and Novartis are developing vaccines using novel adjuvants, while Iomai has a skin patch to boost vaccine impact. Sanofi said it was also working on different dosing and newer technology as well as adjuvants.
FDA staff expressed concern that patients’ immune response to Sanofi’s vaccine was not as strong as to its seasonal flu counterpart. It was not known whether there was any specific effect on women, minority ethnic groups, and those who had seasonal flu shots.