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Controversy Surrounds Success of HIV Vaccine in Thai Study

By L. K. Regan

Last month, researchers from the US and Thailand released results of a three-year study of a combination HIV vaccine that yielded the first-ever positive results. Now those results have been fully published, and scholars and activists alike are arguing over their significance.

When they released their initial results last month, the researchers reported that the new vaccine, which combines two drugs that had failed in previous trials, reduced infection by 31 percent over a placebo. This is a large percentage—but it represented a small absolute number. Of the 8,200 people who got the vaccine, 51 became infected—a mere 23 fewer than the 74 who became infected after receiving a placebo (this was not including seven people determined to have already had HIV at the start of the study). This was, the researchers acknowledged at the time, a barely statistically significant result.

Now, with the release of the full study, that result has been modified yet further. The originally reported results were the outcome of only one of the three methods of statistical analysis applied in the study. The full results, published in the New England Journal of Medicine, add two further analyses that yield a slightly less positive result, in both cases to around 26 percent. This comes along with a 16 percent chance that the results were due to chance, and despite the fact that, as the New York Times reports, five percent would be the usual floor for a vaccine in clinical trials.

All of this has set off a storm of disagreement over appropriate statistical analysis and, in a broader sense, the floor for efficacy in an HIV vaccine, given that no other vaccine in any trial has shown any positive result. For some ADIS activists, the vaccine study has been yet another example of false promises on HIV/AIDS research. "When this was rolled out a couple of weeks ago, it was terribly hyped by the investigators," said Gregg Gonsalves, an AIDS activist. "Some people think you have to dangle the slimmest morsels of hope in front of the general public in order to keep them interested in an AIDS vaccine. But I think that damages the credibility of the effort." On the other side of the discussion, the medical community points out that this vaccine is not marketable as is—but it seems important as an avenue to future research methods. In the words of Raphael Dolin of Harvard Medical School, in an editorial accompanying the study in the NEJM, "Although the merits of each type of analysis can be debated, all three yielded a possible, albeit modest, effect of the vaccine in preventing HIV infection." And, for Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, which paid for much of the $105 million study, "This is a modest effect at best, but I believe it has relevance and is a real effect that needs to be built upon."

Buried in the study's results were other bits of information that may be more troubling to the gay community than the statistical analysis arguments. For instance, the vaccine was most effective for people who became infected through heterosexual sex, or by sex with a single partner. It had a far lower protective function for men who had sex with men, or for intravenous drug users. While researchers are hopeful that these offshoot results could lead the way to future research efforts, they do suggest that a panacea vaccine is still distant.