VaxGen’s Claims of Efficacy in Black and Asian Participants Are Misleading and Premature
24 February 2003The undersigned community-based HIV/AIDS organizations are deeply concerned by today’s presentation of data from the phase III clinical trial of VaxGen’s HIV vaccine candidate, AIDSVAX. While the overall result demonstrates a clear and disappointing lack of efficacy, VaxGen has chosen to spotlight several subgroup analyses that were not part of the statistical evaluation described in the original trial protocol. Specifically, the company claims that the vaccine showed an efficacy rate of 67% in people categorized demographically as Black, Asian or “Other” and an even greater efficacy rate of 78% when results in Black participants were analyzed separately.
These results should be treated with extreme skepticism until subjected to a detailed, independent scientific evaluation.
We fear that VaxGen has deliberately emphasized these putatively positive findings (on the CNN Financial News Network, VaxGen CEO Lance Gordon described them as a “marvelous result”), while failing to emphasize that they are based on very small numbers of infections in a limited sample of participants. This may serve the commercial interests of the company, but it does a great and profound disservice to the HIV-affected communities who must now struggle to make sense of the press stories that the VaxGen release has generated.
The Numbers Game: Reasons to Emphasize Uncertainty
- The smaller the sample size, the less certain the results. Among Black trial participants, there were 9 infections out of 111 placebo recipients compared to 4 infections out of 203 vaccine recipients. A small difference in these rates would erase the statistical significance of this finding. VaxGen strongly implies this result is meaningful by stating that there is a less than 2% possibility that it occurred by chance; however, that does not prove that the explanation lies with receipt of the vaccine.
- When considered separately, differences in the infection rates between placebo and vaccine recipients among Asian participants and those categorized demographically as “Other” were not statistically significant. Only the arbitrary grouping together of these demographic categories with Black participants allowed VaxGen to claim a 67% reduction in infection rate “among ethnic minorities, other than Hispanic individuals” (VaxGen Press Release, 2/24/03).
- Women in the trial experienced a lower infection rate than men, and women were over-represented among the non-White, non-Hispanic populations in the trial. A breakout of the trial results for women in the different demographic groups has not yet been presented.
While the desperate need for an HIV vaccine is clear, especially among the underserved communities that bear the brunt of the pandemic, hope cannot take flight on the gossamer wings of dubious subgroup analyses. It is critical that the scientific leads that may be contained in the VaxGen data are vigorously pursued, but the uncertainty associated with the results presented today must be clearly articulated.
We call on VaxGen to submit the findings to a panel of outside experts assembled by the National Institutes of Health for a full examination of the data and report to the public within 30 days.
AIDS Vaccine Advocacy Coalition (AVAC)
Gay Men’s Health Crisis (GMHC)
Treatment Action Group (TAG)