Scientists Puzzle Over Minor Success of AIDS Vaccine

By David Brown
Washington Post Staff Writer
Friday, September 25, 2009

An experiment in Thailand involving more than 16,000 men and women has demonstrated for the first time a small but measurable protective effect of an AIDS vaccine.

The vaccine, a complicated mixture of six "prime" and "booster" shots, reduced a person's risk of becoming infected by about one-third compared with people getting placebo injections.

The results were barely significant on statistical grounds, perplexing for scientific reasons and unanticipated by most researchers. Nevertheless, the first positive result for an AIDS vaccine after two decades of experimentation is being called a milestone.

"Conceptually, we now know a vaccine is possible," said Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, which paid for most of the six-year trial. "Whether the vaccine is going to look anything like this one I don't know. But at least we know it can be done."

The vaccine is not licensed or being produced in large amounts. It is unlikely -- but not impossible -- that any country would consider it effective enough to be used as a public health measure against HIV.

Instead, the chief usefulness of the "ALVAC-AIDSVAX" vaccine is likely to be what it can teach virologists about what is happening in the immune system when a person is even somewhat protected from HIV.

"We really need to go through the data to see if there are effects here that are potentially useful," said Col. Jerome Kim, a physician involved in the study, which was run by the U.S. Army, the National Institutes of Health and Thailand's Ministry of Public Health.

He predicted that information gained from the trial after the results are fully analyzed will have "important implications for the design of future HIV vaccines."

Other researchers were less sanguine about the study but did not want to be quoted by name as being skeptical when only a few details of the results have been released.

"I just think it's too early really," said one, who spoke on the condition of anonymity for that reason. "It is in a kind of gray zone, and I think we should really get the data and look at it and see what it all means."

That the vaccine is at least nominally a success comes as a surprise.

Early in the decade, more than 20 prominent researchers wrote an open letter to the journal Science urging the federal government to cancel the Thai trial because the vaccine was so unpromising. The study cost $105 million, most of it provided by the National Institutes of Health.

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