The US vaccine developer VaxGen today announced that a phase III study of AIDSVAX adapted for Thailand has failed to show that the vaccine protected against HIV infection during three years of follow-up.
2,546 injecting drug users were randomised to receive either the AIDSVAX product, which is designed to protect against HIV-1 subtypes E and B, or a placebo. The same proportion of people became infected with HIV in the AIDSVAX group and the placebo group (3.1% per year).
Earlier this year VaxGen announced the results of a phase III study using a subtype B HIV vaccine in the United States. That study showed no protective effect in the overall study population, but a suggestion that the vaccine might protect African-Americans and Asians.
The company was widely criticised for its interpretation of the results, and when statistical experts from the US National Institutes of Health and other institutions carried out further analyses, they found that the apparent protective effect may have been an effect of the way in which the analysis was carried out. They found that the chance of finding a statistically significant result within a subgroup increased as the number of analysed subgroups rose. The NIH-led panel concluded that the result was “likely to be spurious” (for further information about this debate, see the recent report in TAGline, the newsletter of the Treatment Action Group).
The results of VaxGen’s Thai study are likely to undermine further interest in vaccine regimens that include gp120 (the HIV protein used in the AIDSVAX), including a proposed NIH study of a gp120 vaccine used as a booster after a canary pox-based vaccine (designed to elicit cellular immune responses to HIV).
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Preventive vaccines against HIV infection
Recombinant sub-unit vaccines (the class of vaccines that includes AIDSVAX