A shot of reality for HIV-vaccine news

International media pounced on the news of the HIV-vaccine study in Thailand, some providing enough data to show the true significance of the results, fewer alluding to the controversies that surrounded this trial from the start. The claim that the vaccine is 31.2% effective is based on 23 fewer cases of HIV contracted over 6 years by the 8,000 Thais who received the vaccine, compared to the 8,000 who received a placebo, or dummy injection. In absolute terms, this is a reduction in risk from roughly 9 tenths-of-one-percent to 6 tenths-of-one-percent, or less than one-half-of-one-percent. That may be a heartening finding, and certainly better than no protection at all. But perhaps pronouncements of an "..aids vaccine breakthrough!" were overly enthusiastic.

Also called "prime-boost," the $119 million trial is testing a combination of two previously unsuccessful HIV vaccines: ALVAC (manufactured by Aventis Pasteur) to "prime" the immune system, and AIDSVAX (developed by VaxGen) to "boost" immunity. Previous tests failed to find any protection from either vaccine alone.

Controversy surrounded this trial from the start. Opponents felt there was no data indicating that a so-called "phase III" trial of this magnitude would be successful, and that a much smaller study could test the hypothesis that the combination might work better than its constituent parts alone. They feared that conducting such a large study without a reasonable assumption of success would waste resources and undermine public and policy support for such health research in the future. (A previous attempt to conduct the trial in the United States had failed to receive support.) Other concerns emerged: Researchers decided after the trial began that reductions in viral load among vaccinated patients who were infected could also count as success, and VaxGen was paid $3 million for supplying its vaccine (pharmaceutical manufacturers typically aren't paid by researchers for unapproved medicines, since they have much to gain should their products prove effective.

Proponents of the trial fired back that existing data did justify the trial, and that even if results found no health benefits from the combo, there was a lot to learn from the exercise.  Differences of opinion aren't new, and often healthy to the scientific process. This tiff was somewhat novel in that it played out on the pages of Science, a highly respected publication, over several months. (A co-author of one letter supportive of the trial that I was able to contact expressed guarded optimism about the new findings.)

Regardless of the eventual outcomes of the trial, prime-boost researchers deserve credit for the unusual team they assembled, which includes the U.S. Army and National Institutes of Health, Sanofi Pasteur and VaxGen, The EMMES Corporation, Thailand's Ministry of Health and Mahidol University, the Royal Thai Army Medical Department, and the Henry M Jackson Foundation. It's not often that you see the armed forces and government departments from two countries collaborating with the private sector and academia to conduct health research. But we'll have to wait a while to see whether final results justify their efforts.