U.S. Army and Thai researchers announced to great fanfare last month that a combination vaccine had produced a statistically significant 31 percent reduction in new HIV infections in a trial of more than 18,000 people in Thailand — a modest rate, but it is the first vaccine whose results that suggested it eventually might be possible to produce a vaccine against the deadly infection, which has killed more than 25 million people.
In an unusual approach, the researchers decided to make the results public in a news conference rather than wait for formal publication of their findings. The complete results have yet to be made public.
Now, however, a secondary analysis of the results have suggested that the vaccine was not quite as good as people had believed, reducing infections by only 24 percent, according to researchers who spoke with Science magazine. The first analysis included all 16,000 people who participated in the trial and produced the promising results. The secondary analysis, which was part of the protocol and is considered normal for all vaccine trials, excluded patients who did not follow the experimental regimen. When that was done, the results were less convincing, according to experts who have seen the data.
The study was criticized when it was launched three years ago because each component of the combination vaccine had failed individually in previous trials. But the National Institute of Allergy and Infectious Diseases, which largely funded the $120-million trial, hoped that it would provide some insight into the kinds of biological responses that must be provoked by a vaccine for it to provide protection.
The National Institute of Allergy and Infectious Diseases is a part of the U.S. Department of Health and Human Services.
The researchers subsequently have been criticized for how they released the results, but they say that they feared the results would be leaked before they presented them and that they hoped to pre-empt such an event.
Full details of the trial are expected to be made public Oct. 20 at a meeting in Europe, and the researchers say they are writing a paper to be submitted to the New England Journal of Medicine.