Researchers may have to release the vaccine early if an epidemic emerges before testing is complete.

Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, said that even though the vaccine has only undergone preliminary testing, it could be used on an emergency basis if a pandemic developed.

Still, it will be several months before the vaccine is tested further and, if licensed, offered to the public on a large scale, the paper said.

"It's good news," Fauci said. "We have a vaccine."

Race Against Time

The bad news, Fauci added, is that "we don't have all the vaccine we need to meet the possible demand.

The critical issue now is, "Can we make enough vaccine, given the well-known inability of the vaccine industry to make enough vaccine?"

Researchers in countries including Australia, Canada, France and Japan have been racing to develop a vaccine against the A(H5N1) strain that is spreading among birds throughout Asia and Russia.

Infectious-disease experts worry that if the strain mutates and combines with a human flu virus to create a new virus, it could potentially kill tens of millions of people worldwide. The last great pandemic, the Spanish flu outbreak of 1918-19, killed an estimated 50 million people around the world.

Tens of millions of birds have already died from infection with the avian flu virus, as well as from culling to prevent the virus' spread.

About 100 people have been infected, and about 50 have died from the bird flu strain. So far there has been no sustained human-to-human transmission, the newspaper said.

As of Friday night, according to the World Health Organization, the avian strain had killed 57 of the 112 people it had been known to infect in four countries. They are Cambodia (four cases), Indonesia (one case), Thailand (17 cases), and Vietnam (90 cases), according to the newspaper.

Early Vaccine Release?

US government researchers and others developed the new vaccine, which is produced by the French drug company Sanofi-Pasteur.

The federal government could decide to release the vaccine under emergency conditions if an avian flu pandemic struck before the testing process was complete, the Times said.