A clinical trial of an HIV vaccine in South Africa by the US National Institutes of Health has been stopped, as it was found ineffective in preventing transmission of the virus. An analysis in January by the National Institute of Allergy and Infectious Diseases, based in Bethesda, Maryland, found that the risk of infection was no different for participants who received the vaccine than for those who were on placebo. The 18-month Phase III trial included 5,400 sexually active men and women between the ages of 18 and 35.
The same vaccine regimen had been tested earlier in a separate Phase III trial in Thailand, which showed a promising HIV reduction rate of 31 percent. However, Thailand’s population has a low to moderate risk of HIV infection, and the South African trial was intended to verify the efficacy of the vaccine in a high-risk population.
The researchers intend to keep track of participants in the clinical trial and collect follow-up information for an unspecified period.