(CNSNews.com) - A special vaccine to protect people against AIDS does not appear to be effective in the general population, but may be effective among blacks and Asians, according to an announcement Monday by the company that developed the drug.
Shares of VaxGen, Inc., a Brisbane, Calif.-based biotechnology company, fell 63 percent Monday after company executives announced that AIDSVAX, a drug it has been working on for years to combat the HIV virus, had failed to protect most at-risk users.
"When all volunteers were analyzed, the vaccine did not appear to be effective," Dr. Michael Para, a principal investigator in the 36-month study, told reporters in a conference call.
When all volunteers were broken down by race and ethnicity, the white and Hispanic groups showed no evidence of vaccine efficacy, Para said.
"On the other hand, the black, Asian and other sub-group showed clear evidence of vaccine efficacy, with an efficacy of 66.8 percent. From the smaller group, just the black volunteers were considered. We see a vaccine efficacy of 78.3 percent. Both of these are highly significant," he said.
The study volunteers included 5,108 men who have sex with men and 309 at-risk women, all of whom were meant to be HIV-negative when they joined the trial, the company said.
Overall, there were just 3.8 percent fewer HIV infections in a group that was vaccinated as compared with those who received a placebo, the company said.
The volunteers received regular counseling to avoid risks that could lead to HIV infection and were advised to assume they may have received a placebo and that the vaccine might not be effective, the company said. The trial was conducted in the United States, Canada, Puerto Rico and the Netherlands.
But researchers said they were encouraged to find unexpected signs of effectiveness in 498 non-white volunteers, including blacks and Asians. The expected infection rate for the 314 black volunteers who received the vaccine was reduced by 78 percent.
Company officials said it was too early to tell, however, if the findings offer hope for 28 million people in sub-Saharan Africa who are infected with HIV, the virus that causes AIDS.
Bill Arnold, chairman of the AIDS Drug Assistance Program Working Group, a Washington-based coalition of pharmaceutical companies and AIDS advocacy organizations, said work on finding a vaccination will continue.
"I think everybody is somewhat disappointed in the results so far of the VaxGen trial, but we shouldn't let this discourage us and we should keep going because sooner or later we'll need either a version of VaxGen or something else," he said.
It's not unusual for multiple trials to fail before researchers get a breakthrough, Arnold said. "And there are no shortcuts. We have to keep after it; we have no choice."
Pat Christen, executive director of the San Francisco AIDS Foundation, cautioned against premature interpretation of VaxGen's study.
"We support VaxGen's intention to work closely with the Food and Drug Administration to scrutinize their data and determine whether further trials are warranted and necessary," Christen said in a release.
"However, until the data is crunched and the analyses are finished, it is completely premature to determine whether or not AIDSVAX is truly effective for particular populations," he said.
E-mail a news tip to Lawrence Morahan.
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