The two vaccines are called ALVAC and AIDSVAX. ALVAC contains canarypox -- a bird virus that has been genetically altered so it can't cause disease in humans -- to transport synthetic versions of three HIV genes into the body. AIDSVAX contains a genetically engineered version of a protein on HIV's surface. Because the vaccines aren't made from a whole virus -- either dead or alive -- they can't cause AIDS, according to the AP.
The study was done in Thailand because U.S. Army scientists did key research in that country when the AIDS epidemic emerged there, isolating virus strains and providing genetic information on them to vaccine makers. The Thai government also strongly supported the idea of doing the study, the AP reported.
For the trial, half of the 16,402 volunteers were given six doses of the two vaccines in 2006 and half were given placebos. They then got regular HIV tests for three years. Fifty one of those who got the vaccines became infected compared to 74 who were given placebos, the Times said.
Although the 31 percent reduction in rates of infection was modest, Col. Jerome H. Kim, a doctor who manages the U.S. Army's HIV vaccine program, called the finding statistically significant. And, he added, it's "first evidence that we could have a safe and effective preventive vaccine," AP reported.
The Thais chosen for the study were a cross-section of that country's young adult population, not just high-risk groups like intravenous drug users or sex workers, Kim added.
One curious finding showed that the vaccine induced very few antibodies. Most vaccines consist of parts of a virus or bacterium that prompt the immune system to make antibodies, which then protect the body by attacking the invading pathogen.
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