Merck is beginning critical human trials for a vaccine that could prevent or decelerate HIV/Aids infections.

Merck said yesterday it has begun enrolling an expected 1,500 volunteers globally to test the vaccine in people with a high risk of contracting HIV. The study is in collaboration with the HIV Vaccine Trials Network (HVTN), which is supported by the US government-funded National Institutes of Health, at sites in North and South America, the Caribbean and Australia.