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Canceled Vaccine May Have Boosted HIV Risk SARAH RUBENSTEIN and MARK SCHOOFS SEATTLE -- New evidence suggests that Merck & Co.'s experimental HIV vaccine may have made its recipients more vulnerable to the deadly AIDS virus -- and has prompted researchers to warn participants in other trials that similarly made vaccines for a range of other diseases might also increase their susceptibility to HIV. Merck canceled development of its HIV vaccine in September after it became clear in a clinical trial that it didn't prevent infection or reduce the amount of HIV in subjects who became infected. Since then, Merck and its partners have analyzed data from the 3,000-participant trial and found the damage may be deeper: In a large subset of participants, those given the vaccine acquired HIV at a higher rate than those who received a placebo. All participants were HIV-negative at the start of the trial. Scientists presented their analyses yesterday in Seattle at a conference of the HIV Vaccine Trials Network, or HVTN, which co-sponsored the trial with Merck. The trial was conducted in North and South America, the Caribbean and Australia. A second trial in South Africa has also been stopped.
The Merck vaccine, which includes only a few synthetic fragments of HIV loaded onto a genetically modified cold virus, called an adenovirus, couldn't itself infect patients with HIV. Instead, the vaccine might have altered the immune system to facilitate infection. Some researchers are concerned that other vaccines made with the adenovirus could have the same effect. Scientifically, the failure of the Merck vaccine will make researchers "relook at everything," says Anthony Fauci, a veteran HIV researcher and the director of the National Institute of Allergy and Infectious Diseases. He says scientists will likely re-examine myriad issues, from the animal models used to test a vaccine before it is tried in humans to the blood tests used to determine if a vaccine is stimulating the immune system. The National Institutes of Health, which helped sponsor Merck's aborted clinical trial, recently paused recruitment for vaccine trials involving several diseases, including Ebola. Those vaccines, like the failed Merck one, are made with an adenovirus, says Gary Nabel, director of the NIH's Vaccine Research Center. The NIH trials are expected to continue, but researchers want to advise subjects of the potential risks, Dr. Nabel says. In addition, researchers will meet next month to rethink whether and how to change a future NIH trial of an HIV vaccine constructed from an adenovirus.
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