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An AIDS vaccine, which has been in phase III trials for the past three years, has failed to show a significant reduction in the development of HIV among the those who were vaccinated, the manufacturer, VaxGen, has announced.
But the vaccine has shown a significant reduction in certain ethnic groups, indicating that black and Asian volunteers may have produced higher levels of antibodies against HIV than white and Hispanic volunteers.
The full trial results are to be presented later this month at a symposium on HIV and will then be analysed by the US Food and Drug Administration.
In all, more than 5000 people took part in the randomised, double blind, placebo controlled trial, which took place in the United States, Canada, Puerto Rico, and the Netherlands. Volunteers included 5108 gay men and 309 at risk women. All were HIV negative when they joined the trial. In all, they received seven injections over the three year period.
The initial results are based on volunteers who received the primary course of three injections (of the vaccine or placebo) over the first six months; 3330 volunteers received the AIDSVAX B/B injection and 1679 received placebo.
At the end of the three year period, the percentage of volunteers developing HIV was 5.7% in the vaccine group and 5.8% in the placebo group.
Among ethnic minorities excluding Hispanic volunteers, however, there were 67% fewer HIV infections in those receiving the vaccine than in those receiving placebo (P value <0.01; n=498). And among black volunteers this reduction rose to 78% (P<0.02, n=314).
The size of these two groups, however, is small. The vast majority of volunteers were white (4185); 326 were Hispanic and 498 non-white (black, Asian, and other); only 314 were black. In the non-white group, 17 of the 171 (9.9%) volunteers given placebo became infected, compared with 12 of the 327 (3.7%) given the vaccine. Among the black volunteers, 9 of the 111 (8.1%) given placebo became infected, compared with only 4 of the 203 (2%) given vaccine.
The vaccine is made up of a recombinant form of the protein (gp120) found on the surface of HIV. These genetically engineered proteins mimic the two strains of HIV subtype B antigens that are prevalent in the strain of the virus found in North America, Europe, Australia, Japan, and Puerto Rico.