AIDS Vaccine Prevents Some HIV Infections

Researchers say that a new AIDS vaccine is somewhat protective against the strain of HIV that is circulating in Southeast Asia. The vaccine, which combines two earlier vaccines that failed to protect people, was 31 percent effective in a Thai study. Experts say the finding is significant progress toward developing a vaccine that might be successful one day.

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ROBERT SIEGEL, host:

From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.

MADELEINE BRAND, host:

And I'm Madeleine Brand.

We begin this hour with news about an experimental AIDS vaccine. It's the largest study ever done on humans on an AIDS vaccine, and the tests were done in Thailand. The results? Surprising. The vaccine provided modest protection against HIV infection. Scientists say that small success marks the first time any vaccine has ever shown any protective effect in humans.

NPR's Richard Knox reports.

RICHARD KNOX: AIDS vaccine researchers have been so frustrated for so long that they're saying this modest advance is an important milestone. Dr. Jerome Kim is one of the study's leaders.

Dr. JEROME KIM (Walter Reed Army Institute of Research): Our field has been marked by the failure of a number of significant trials, and people were concerned that we might not ever have a vaccine, an HIV vaccine, that prevented this infection. And, you know, here we had the first-ever vaccine study to reduce the risk of HIV infection in humans.

KNOX: The U.S. government put up $105 million for the study. More than 16,000 young adults in Thailand volunteered for it in 2003. Half got the experimental vaccine regimen. Actually, it was a combination of two different vaccines, neither of which had shown much promise by itself. The other half got injections of an inactive placebo. The volunteers were tested for HIV infection for three years. Dr. Kim says the results were ready only three weeks ago.

Dr. KIM: The group of collaborators were sitting in the room; we didn't have an inkling. We had no clue, and there was a fair amount of tension.

KNOX: The tension broke when the statisticians revealed that 51 people in the vaccine group had gotten infected with HIV, compared to 74 who got the placebo. That's a 31 percent difference. Not a home run by any means, but Kim says the group is excited.

But when the researchers looked at the results more closely, they started scratching their heads. As Kim puts it…

Dr. KIM: We don't know why we got the result that we got.

KNOX: In particular, they don't understand why the vaccine had no effect in the 51 people who got HIV even though they got the vaccine. They thought one component would at least blunt in the infections that did occur. Opponents of AIDS vaccine research say the new vaccine is not likely to be widely used in people. Dr. Seth Berkley heads the International AIDS Vaccine Initiative.

Dr. SETH BERKLEY (President and Founder, International AIDS Vaccine Initiative): We have to remember that this protection, although very exciting in humans, was, you know, 31 percent. We're going to want to improve dramatically upon it. And my guess is that this is more of a steppingstone than this is the final candidate.

KNOX: That is, it'll generate a lot of new science to explain how the combination of two relatively unpromising vaccines produced any protection at all. Scientists may also try to customize this vaccine for Africa, where different strains of HIV are circulating. Dr. Josh Ruxin, of Columbia University, heads an AIDS project in Rwanda.

Dr. JOSH RUXIN (Assistant Clinical Professor, Mailman School of Public Health, Columbia University): What this does is it keeps hope alive, it rekindles optimism that yes, there is someday going to be a vaccine; that really is conceivable.

KNOX: But clearly, Ruxin says, this is not that vaccine.

Richard Knox, NPR News.

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