Voice of America - October 26, 2007
Scott Bobb
Johannesburg

Human trials of a promising AIDS vaccine in South Africa have been halted prematurely after studies of sister trials in North America confirmed that the vaccine did not prevent HIV infection. Correspondent Scott Bobb reports from our bureau in Johannesburg that as a result the 800 volunteers who had already enrolled in the trial have been called in for more counseling.

The chief investigator for the AIDS vaccine trials in South Africa, Glenda Gray, says the study's independent monitoring board ended the program after several weeks of review.

"They [the board] decided that there was no use in continuing our study because the vaccine did not protect against HIV infection," she explained. "And it also looked like that there may be a possibility the participants that received the vaccination may have increased susceptibility to acquiring HIV infection through high-risk behavior."

The vaccine was considered one of the most promising to date and had passed preliminary trials that determined it was safe and boosted the immune system.

Researchers say the vaccine itself could not cause HIV infection, because it uses only a few parts of the DNA from the virus that causes AIDS and these were synthetic.

During the trial, one-half of the human volunteers was to be given three injections of the vaccine while the other half was to receive injections with no vaccine, called a placebo.

The volunteers did not know whether they were being given the vaccine or not. But all were counseled to maintain safe sex practices because the drug was experimental.

Gray says researchers discovered in September that in the American trials 19 volunteers out of 672 who were given two doses of the actual vaccine became infected with HIV, while only 11 of 691 who were given the placebo became HIV positive.

She notes that there were some differences in the two studies. The American study focused primarily on gay men. The South African study, which began earlier this year, focused primarily on heterosexuals and included for the first time many women. Nevertheless, it was decided to end the South African trial out of concern for the heath of the volunteers.

The 800 volunteers who had been recruited out of a projected total of 3,000 are being called in and being counseled to continue safe sex practices and continue with their free testing.

"We are all very disappointed that this vaccine product didn't work," she said. "But we do hope that it's going to open up a door, a window of opportunity for us to understand better what is going on with this virus as it interacts with the immune system."

She says some volunteers who had received the vaccine have expressed dismay upon learning that they might be more susceptible to HIV infection. But, she says others have shown remarkable optimism saying they want to volunteer when the next trials are announced.

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