A promising experimental vaccine to prevent the AIDS virus has failed in a crucial experiment, with volunteers becoming infected with HIV anyway, leading the drug developer to halt the study.
Merck & Co. said Friday that it is ending enrolment and vaccination of volunteers participating in the international study, which is partly funded by the National Institutes of Health (NIH).
Officials at Merck told the Associated Press that 24 of 741 volunteers who got the vaccine in one segment of the trial later become infected with HIV, which causes AIDS.
In a comparison group of volunteers who got dummy shots, 21 of 762 participants also became infected with HIV.
"It's very disappointing news," said Keith Gottesdiener, head of Merck's clinical infectious disease and vaccine research group. "A major effort to develop a vaccine for HIV really did not deliver on the promise."
The study volunteers were all free of HIV at the start of the experiment. But they were at high risk for getting HIV: most were homosexual men or female sex workers. They were all repeatedly
counselled about how to reduce their risk of HIV infections, including use of condoms, according to Merck.