Important note: Information in this article was accurate in 2007. The state of the art may have changed since the publication date.
San Francisco Chronicle - November 14, 2007
Sabin Russell, srussell@sfchronicle.com.
Leaders of the study, including representatives of vaccine manufacturer Merck & Co., the National Institutes of Health, and a network of doctors who enrolled the volunteers decided Monday to "un-blind" it after lengthy discussions in Seattle last week.
Because the early results of the trial showed that vaccinated volunteers might be at higher risk of contracting HIV, there was a compelling ethical case to tell participants whether they were assigned the vaccine or placebo. However, by un-blinding the study, researchers will be limiting the scientific value of any data produced as they follow participants in the coming years.
"It's very important that we follow up with the study volunteers," said Dr. Susan Buchbinder, director of HIV Research for the San Francisco Department of Public Health, and co-chair of the committee that set up the protocols for the trial.
One hundred thirty-seven of the trial participants live in the Bay Area.
Although the study showed definitively that the vaccine did not protect against HIV infection, the early trend showing increased risk among the vaccinated was not proven. So far, 49 of the 1,500 volunteers who received the vaccine have become infected, compared with 33 among a similarly sized group given a placebo.
In addition, 21 of those infected in the vaccinated group also tested positive for prior exposure to a common cold virus, which was used in hobbled form as a component of the vaccine. Only nine of those in the placebo group who showed prior exposure to the cold virus were infected.
Buchbinder said researchers don't know why the vaccinated group had an apparently higher infection rate, but one possibility is simply chance - and that over time, the number of infections in both groups would level out.
The San Francisco AIDS physician said she agrees with the decision to un-blind the study.
"At the meeting in Seattle on Thursday, there was lots of opportunity for discussion among the investigators and the community, and the vast majority were in favor of un-blinding," she said.
The alternative would have been to allow any participants to be told whether they received the vaccine if they asked to know, but many researchers concluded that there would be little extra information gained by this strategy of "voluntary un-blinding."
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