The University of Maryland School of Medicine and two other institutions next week will begin human tests of a vaccine designed to combat avian influenza - widely feared for its potential to cause the next global pandemic .
The vaccine is designed to prevent a flu strain known officially as H5N1, which jumped from birds to humans after it was first identified in Hong Kong in 1997. Since then, there have been at least 69 confirmed cases and 46 deaths, none in the United States.
Dr. Anthony S. Fauci, head of the National Institute of Allergy and Infectious Diseases, told microbiologists gathered in Baltimore yesterday that the government has stockpiled the equivalent of 2 million doses of the untested H5N1 vaccine at a cost of $13 million in case of an outbreak here or overseas.
Distributing the vaccine would require clinical trials and a series of federal regulatory approvals. But Fauci said ordering the drug in bulk ahead of time from Sanofi Pasteur of Swiftwater, Pa., provides a safety cushion in case of an outbreak and makes it easier for the manufacturer to produce more doses if they're needed. "It's very likely the H5N1 vaccine will be found to be safe," he said.
Fauci and medical school researchers announced the trials at the annual Biodefense Research Meeting sponsored by the American Society for Microbiology at the Baltimore Marriott Waterfront.
As a first step, researchers at the University of Maryland School of Medicine will begin recruiting volunteers next week to test the vaccine. Clinical trials will also be conducted at the University of California, Los Angeles and the University of Rochester. Researchers at each medical school seek 150 healthy adults. Participants will be given two shots of the vaccine a month apart, with their health monitored in followup visits and phone calls, according to Dr. James Campbell, an assistant professor of pediatrics at the UM medical school and principal investigator here.
To develop the vaccine, scientists used an inactive strain of avian flu taken from a Vietnamese patient in February 2004. Campbell said there are no live flu cultures in the vaccine, and there is no risk of volunteers contracting H5N1 from the injections or spreading it to others. "The vaccine has no virus in it, so you can't get the virus from it," he said.
Fauci said a vaccine for H5N1 could help prevent a global pandemic. To date, H5N1 has spread from Hong Kong to at least nine other Asian countries and has been found in cats, pigs, ducks, chickens and humans. In contrast with other flu strains, humans have never developed H5N1 antibodies because they've never been exposed to it.
"The host range of H5N1 is not restricted. It's spreading, and that's a very bad sign in the evolution of microbes," Fauci told the researchers.
Federal officials last year announced the awarding of H5N1 contracts to two manufacturers. Along with Sanofi Pasteur, Chiron Corporation of Emeryville, Calif., is developing a vaccine that will be tested in clinical trials this year, Fauci said.
In a separate interview, Fauci said the vaccine program is part of an overall effort to keep H5N1 and other flu strains in check. His agency, part of the National Institutes of Health, spends about $120 million on flu research. "I wouldn't say I'm sounding an alarm, but I want people to be aware of the seriousness of the situation so we can address it with an effective response," he said.
Other government efforts include genetic experiments by the Centers for Disease Control and Prevention, where scientists are trying to determine what would happen if H5N1 and the human flu virus were to combine. Those results will not be known for some time.
Global flu epidemics, known as pandemics, tend to occur every generation or so and involve different strains of the virus. The most lethal in modern times, known as the Spanish flu, began in 1918 and claimed from 20 million to 100 million lives worldwide.
Health officials say there is no way of knowing for sure what strain will cause the next pandemic, but H5N1 is a likely candidate. "It's out there, and there's no immunity in the general population to it," Fauci said.
Human-to-human spread of H5N1 is rare. Most victims are infected by contact with diseased birds, but because flu viruses can mutate, scientists say H5N1 could develop the ability to spread among humans.
Health officials are particularly concerned about a report this year, in the New England Journal of Medicine, of an 11-year-old Thai girl who caught the virus from infected chickens and then apparently transmitted it to her mother and an aunt who had been caring for her. The girl and her mother died, while the aunt survived a severe bout of the illness.
"This is one case of great concern that we're monitoring very, very carefully," Fauci told the microbiology conference.
Investigators caution that in the Thai case, they found no evidence that the disease spread beyond the immediate family. But they fear it demonstrates that avian flu might be developing the ability to spread through human contact.
Immunizing the masses
In the UM trial, participants will be required to keep journals to record any side effects from the vaccine. Participants will be paid up to $530, and their health will be monitored for seven months, Campbell said. Future H5N1 clinical trials at the medical schools will examine its effects on children and the elderly.
There is no way to know how soon either vaccine will be approved for mass marketing. Such approval usually takes two to five years. But the time could be shortened, depending on how fast the disease spreads internationally. "If this vaccine is found to be safe and we see the right immune response, things could move faster," Campbell said. " I think people, knowing how bad a pandemic would be, would be willing to take on the small risks involved."
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