SAN FRANCISCO – An experimental AIDS vaccine being developed by VaxGen Inc. does not appear to protect most people from the disease, but does show promise in protecting blacks and Asians, the company said.
The overall expected rate of infection was not reduced in the high-risk people who volunteered to take the vaccine, VaxGen 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 night. "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.
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.
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.
Experts believe a vaccine is the only way to stop the worldwide AIDS epidemic, which has already killed 20 million people and infected 40 million more.
Merck & Co. is developing a different type of vaccine that has showed promise in early human testing, but researchers caution they are still years away from proving whether it works.