AIDS vaccines

AIDS vaccines

A new AIDS vaccine tested on more than 16,000 volunteers in Thailand has protected a significant minority against infection, the first time any vaccine against the disease has even partly succeeded in a clinical trial. Scientists said they were delighted but puzzled by the result. The vaccine — a combination of two genetically engineered vaccines, neither of which had worked before in humans — protected too few people to be declared an unqualified success. And the researchers do not know why it worked.

“I don’t want to use a word like ‘breakthrough,’ but I don’t think there’s any doubt that this is a very important result,” said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, which is one of the trial’s backers. Over the course of three years, 74 of 8,198 people who received placebo shots became infected with HIV, compared with 51 of 8,197 people who received vaccine. So the vaccine appeared to reduce the risk of being infected by 31%. The statement from NIH, one of the sponsors of the trial, called this a “modest preventive effect.”

Patients who received the vaccine and did get infected didn’t have lower levels of virus than patients who received placebo and got infected — a puzzling finding, given that a partially effective vaccine would be expected to help a patient’s immune system fight the disease. Still, previous AIDS vaccine trials have failed miserably. A Merck AIDS vaccine study was halted in 2007, after data showed the vaccine didn’t reduce the risk of infection and may actually have left some people more susceptible to the virus. The NIH subsequently canceled plans for another major AIDS vaccine trial that would have used a similar approach.