Brisbane, California-based VaxGen reported today that its AIDS vaccine -- the first tested in a large population of people at risk for the disease -- has proven to be largely ineffective. AIDSVAX reduced the rate of infection by 3.8 percent in people who received it compared to a control group that received placebo injections. Vaccines need to be at least 70 percent effective in reducing HIV infection to gain approval for widespread use. VaxGen officials had said an efficacy of 30 percent might be enough to make the product useful in some populations.
The vaccine appeared to be effective, however, in a subgroup of subjects, notably African Americans. Among them, 2 percent who received the vaccine became HIV-infected, compared to 8.1 percent of the placebo group -- a statistically significant difference. When Asians and mixed-race volunteers were added to the group of blacks -- a total of about 500 of 5,000 volunteers -- the protective effect was nearly as strong.
"It appears that blacks, Asians and the other non-white volunteers were able to induce a higher level of antibody than others. There appears to be a correlation between that and protection," said VaxGen spokesperson James Key.
While more than a dozen vaccines have been tested in small populations, AIDSVAX was the first one tested in a large, diverse population. It was tested in 5,417 volunteers at high risk for HIV in the United States, Canada, Puerto Rico and the Netherlands. VaxGen is testing a similar vaccine in Thailand; results of that study will be known later this year.
In the study whose results were announced today, about twice as many people received the vaccine as received the placebo. Three shots, spaced three months apart, were given initially, followed by booster shots every six months. Results were limited to 5,009 subjects who received at least three shots. Over three years, 5.7 percent of the people who received AIDSVAX became HIV-infected, compared with 5.8 percent of people who received the placebo shots. All volunteers were counseled to practice safer sex and not to count on protection from the vaccine.
Back to other CDC news for February 24, 2003