TUESDAY, Aug. 9, 2005 (HealthDay News) -- The good news of successful human trials of a vaccine to protect against avian flu was tempered late Monday by official assertions that the vaccine will not be issued like a regular vaccine and certainly will not be deployed at all in the immediate future.
Media reports earlier Monday that the vaccine will be distributed as early as next month were mistaken, said Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, which oversaw the trials.
"We have no plans whatsoever to deploy this vaccine. The vaccine is in the process of clinical trials," Fauci said. "We will order considerably more doses of this and stockpile. We have no plans at all of deploying it under the current circumstances. That is absolutely untrue. There's no plan to deploy or administer it to anybody. We're in a stockpiling model."
Health officials had announced over the weekend that initial tests of a human vaccine against the current strain of avian flu had been successful. The vaccine protects against a single strain of flu virus, designated H5N1, which leads to severe disease in birds and humans.
That strain of avian flu has killed millions of birds in Asia this year, and so far about 50 humans have died from it. Experts fear that if the strain acquires the ability to jump from human to human, the virus, considered more lethal than many other strains, would trigger a pandemic as fearsome as the one that killed 50 million people worldwide in 1918.
Still, there's no evidence thus far that such a threat is emerging.
"No one knows if there will be a pandemic. Influenza virus is very unpredictable," said Dr. Pascal James Imperato, chairman of the department of preventive medicine at SUNY Downstate Medical Center and a former New York City health commissioner. "H5N1 seems to be particularly virulent and spreads very widely in bird populations, but, thus far, transmission has been zoonotic [in animals]. Although they have documented a few cases of human-to-human transmissions, there is no real firm proof that those individuals were not exposed to birds."
In the human trials, which got underway in April, the vaccine produced a strong immune response in 113 of the 452 participants in the study. All of these participants were healthy adults under the age of 65, Fauci said.
"It's just a preliminary result, but it's very encouraging," said Dr. John Treanor, a professor of medicine, microbiology and immunology at the University of Rochester and principal investigator of the tests conducted at that institution. The trial is also being conducted at the University of Maryland School of Medicine and The University of California at Los Angeles.
Treanor added that data on the remaining 330 participants would be analyzed. Researchers are now moving ahead to test the vaccine in more volunteers.
"We're going to move on to elderly people, 65 and greater and, after that, are going to look at the pediatric population," Fauci said. "Simultaneously with that, we will be doing some preliminary studies on dose-sparing strategies. Those things will all be ongoing."
Dose-sparing strategies would be ways to stretch the available supply of vaccine. "Those strategies would include the use of adjuvants, as well as strategies to inject the vaccines into the skin rather than the muscle," Treanor said.
Questions on dosing and side effects, among other things, still need to be answered, the health officials said.
"The preliminary data are encouraging in that the vaccination induces, in a dose-response way, a response that would protect against this particular strain," Fauci said. "The dose that is required to elicit this degree of immune response is considerably higher than the doses that would give comparable response for season flu."
Before the trial even began, the government ordered 2 million doses from French manufacturer Sanofi-Pasteur and is moving ahead with plans to order more.
"We are going to move ahead and negotiate with the company to buy considerably more than the 2 million doses that are currently in a strategic national stockpile, just in case," Fauci said.
And when would the vaccine be used?
"If the virus developed the capability of efficiently going from human to human in a sustained manner," Fauci said. "That would be the trigger point to implement selective vaccinations of the highest-priority people, depending upon how much vaccine we had."
More information
Background on avian flu is provided by the U.S. Centers for Disease
Control and Prevention.
