The government expects to stockpile nearly 8 million doses of an experimental vaccine against pandemic influenza by February, and studies are underway that could stretch that supply to cover more than a third of the population, federal health experts said yesterday.
Two manufacturers are already making doses of the experimental vaccine under contract, and most of them will be delivered to government stockpiles by late December, according to presentations made to an advisory panel of the Health and Human Services Department.
That unusually rapid clip reflects the high priority the Bush administration has placed recently on preparing the nation for a catastrophic flu outbreak. The immediate plan is a start toward building a stockpile that eventually could reach tens of millions of doses, assuming that Congress appropriates enough money.
In the worst case, scientists said, the vaccine being manufactured now would immunize only 4 million people, each of whom would need two shots a month apart. That means the vaccine would probably be restricted to critically needed personnel who would keep the government and public-safety services running during a pandemic. About a quarter of the vaccine is destined for a stockpile controlled by the Pentagon.
A pandemic would be expected to confine millions of people to their homes for weeks or months, shutting down much of the economy.
Techniques to dilute the vaccine while preserving a strong immune response are under study. In the most optimistic scenario, the stockpile due by February might be diluted to cover 120 million people out of a U.S. population of 298 million. Some preliminary research suggests that dilution will work, but scientists said larger studies are needed. How well the vaccine, diluted or not, would prevent influenza in a pandemic remains uncertain.
"I didn't realize there was so much going on," said Charles M. Helms, a University of Iowa doctor and chairman of the National Vaccine Advisory Committee, which heard reports on the government's efforts at a meeting in Washington yesterday. "It's incredible."
William Hall, a spokesman for the Health and Human Services Department, said the government has made it a point not to claim that vaccine dilution would produce a huge stockpile in the short run, since the studies needed to prove that are still underway. "We're trying to stretch the supply of vaccine, but to be perfectly honest, if a pandemic occurs tomorrow, we can cover 4 million people," he said.
A fast-spreading form of influenza that sickens mostly birds but can also kill people has provoked worldwide alarm.
So far the virus cannot jump readily from person to person. But scores of people, mostly in Asia, have caught it from birds, and it has killed half of them. Authorities fear that the virus will evolve to the point that it can spread readily in the human population.
The influenza pandemic of 1918 killed perhaps 50 million people worldwide in months. President Bush announced a plan Nov. 1 to prepare the nation for a pandemic, and Congress is considering his request for more than $7 billion in emergency funds.
There is no licensed human vaccine today, and standard vaccine against annual flu would offer little protection. Several countries, including the United States, are rushing to develop and stockpile a vaccine. The government also is stockpiling Tamiflu, a drug that might be used to treat infected people, but for prevention, a vaccine is the preferred approach.
The effort is fraught with uncertainties, however. The experimental vaccine is designed to immunize people against the viral strain circulating in birds, but it is unclear how much protection it would provide if the virus evolved to spread readily among humans.
Multiple human tests are underway, and Linda C. Lambert, chief of respiratory diseases at the National Institute of Allergy and Infectious Diseases, said researchers would offer some results soon. But scientists do not expect hard data on the number of deaths the vaccine could prevent to be available until a pandemic outbreak.
Sanofi Pasteur SA of Lyon, France, and Chiron Corp. of Emeryville, Calif., are making the experimental vaccine under government contract. Several companies are working on more advanced vaccines that might offer strong protection with one shot, but those are years away.