SAN FRANCISCO (AP) _ A highly anticipated experimental AIDS vaccine failed to protect most people from the disease in its first major trial, although it did show promise in protecting blacks and Asians, its developer said.
The overall expected rate of infection was not reduced in the high-risk people who volunteered to take the vaccine, VaxGen Inc. said late Sunday. However, the expected infection rate for the 314 black volunteers who received the vaccine was reduced by 78 percent _ a finding the researchers said was unexpected. The rate was reduced by 67 percent for all nonwhite volunteers other than Hispanics.
``This is the first time we have specific numbers to suggest that a vaccine has prevented HIV infection in humans,'' VaxGen vice president Phillip Berman said in a prepared statement Sunday. ``We're not sure yet why certain groups have a better immune response.''
The Brisbane, Calif.-based company said it planned to continue developing the vaccine and will examine more closely why it worked better in blacks and Asians than it did in whites and Hispanics.
Experts believe a vaccine is the most promising way to stop the worldwide AIDS epidemic, which has already killed 20 million people and infected 40 million more. Several other vaccines are in development.
The Food and Drug Administration told Vaxgen it would consider approving its AIDSVAX vaccine even if it was only 30 percent effective _ reflecting the urgency of finding weapons against the AIDS epidemic. VaxGen did not manage that reduced threshhold. Most approved vaccines are more than 80 percent effective.
The publicly traded company's stock has risen and fallen dramatically during the last year as rumors of the experiment's results swirled. It sold for as low as $4.81 a share and as high as $23.25. It closed at $13.02 in trading on the Nasdaq Stock Market Friday.
The experiment, which initially involved 5,400 people at high risk for the disease, had been criticized by some activists who say it could encourage risky behavior. Even if the vaccine proved effective on some level, there might be no way to tell if it has worked on a particular individual.
But VaxGen has won widespread praise from doctors and the FDA for its handling of an ethically difficult test. The company counseled patients in the experiments to practice safe sex because the vaccine may not work and because one-third of the volunteers received the placebo.
AIDSVAX works by inducing the immune system to produce antibodies that attach to a protein on the surface of the virus, blocking its ability to infect healthy cells.
The company is also conducting a test of 2,500 intravenous drug-users in Thailand, with results to be released later this year.