THURSDAY, March 24, 2005 (HealthDay News) -- The first U.S. trial of a vaccine against avian influenza, a potentially devastating viral infection, will begin early next month.
The National Institute of Allergy and Infectious Diseases said the vaccine will be given to 450 healthy adults at the University of Maryland School of Medicine, the University of Rochester School of Medicine, and The University of California at Los Angeles.
"We're looking for two results, safety and immune response," said Dr. James Campbell, an assistant professor of pediatrics, who will lead the trial in Maryland.
Safety data will become available almost immediately after volunteers receive the shots, as they are checked for fever and other adverse symptoms. The ability of the vaccine to stimulate an appropriate immune response against the avian flu virus will be assessed in a series of tests over the next seven months, he said.
Health officials are worried about a possible worldwide pandemic of avian flu, which has had an extremely high death rate in the small number of cases reported in southeast Asia.
"In the cases that have been recognized, the case fatality rate is 67 percent, 46 deaths in 69 cases," Campbell said. But there is an ongoing debate about the deadliness of the disease, he added.
"It is possible that people have developed mild avian flu and have not consulted health-care providers," he said. That is especially true because most cases have occurred in rural areas of Vietnam and Cambodia, where health care is not easy to obtain.
"Truthfully, it is too early to tell" how deadly the infection is, he said. "But we should assume that when people seek medical care for it, a high proportion of them will die."
The vaccine protects against a single strain of flu virus, designated H5N1, which leads to severe disease in both birds and humans. "We're very fortunate that there does not appear to be a lot of diversity in the isolates that have been obtained," said Dr. John Treanor, a professor of medicine, microbiology and immunology at the University of Rochester, who is in overall charge of the program. "It looks like a vaccine against a single strain will work."
One major unanswered question is whether avian flu can spread from human to human, Treanor noted. "So far, there have been a very limited number of person-to-person transmissions," he said. "The unpredictable part is whether that will change in the future."
The fear is that easy human-to-human transmission could lead to a worldwide pandemic similar to the flu outbreak that killed an estimated 50 million people in 1919. If avian flu is only a tenth as deadly as the numbers now show, the toll in a global epidemic could be even larger, Campbell said.
"In the 1919 pandemic, half of the world population was infected, and 2 percent of the world population died," he said. "If this virus has anywhere near that effect, it could cause a major social disruption."
More information
Background on avian flu is provided by the U.S. Centers for Disease Control and Prevention.
