U.S. government scientists have developed a vaccine they believe can protect people against the strain of avian flu that has mostly spread in birds through Asia and recently was found in Russia. But, producing large amounts of the vaccine may be a problem.
Tens of millions of birds have died from the avian flu virus or been destroyed by authorities who wanted to prevent the disease from spreading. So far, the virus has not infected humans in large numbers, with the human death toll at around 60. Almost all the cases have been in Asia.
But, health officials are worried the strain could mutate on its own or combine with a human flu virus. This would make human to human transmission easier and could cause a worldwide pandemic.
The director of the National Institute for Allergy and Infectious Diseases, Anthony Fauci, said it is this concern that has prompted U.S. researchers to try to find an effective vaccine for the current strain of avian flu, or H5N1.
"Last year, when we first recognized the potential problem of the H5N1, we developed a vaccine that we just started testing in April of this year," he said. "And we have shown that you can have a dose response curve that induces what you can project would be protective immunity."
Dr. Fauci said that the biggest problem he sees at this point is production.
"We do have a vaccine," he said. "The critical issue is how are we going to scale up the production of that vaccine, because the vaccine-producing capacity is much more the rate limiting factor than is the science of getting an H5N1 vaccine."
An earlier human vaccine against avian flu was prepared after the disease first appeared in the world, in Hong Kong, in 1997. That vaccine was never fully developed or used, and the strain has mutated since then.
With H5N1, a similar problem could exist. Dr. Fauci acknowledged that officials do not yet know the exact strain of avian flu that will cause a pandemic, if it happens.
"That's true, but it's better to have one that's at least related to the virus that's circulating now in Asia than to have none at all," he said.
The vaccine is intended to protect people against infection, not treat those who are already sick.
But despite its promise, the vaccine must undergo additional tests before it can be licensed and before policy makers determine when and how it should be administered.