An experimental HIV vaccine has for the first time cut the risk of infection, according to scientists.
The vaccine - a combination of two earlier experimental vaccines - was given to 16,000 people in Thailand, in the largest ever such vaccine trial, the BBC reports.
Researchers found that it reduced by nearly a third the risk of contracting HIV, the virus that leads to Aids. It has been hailed as a significant, scientific breakthrough, but a global vaccine is still some way off.
The study was carried out by the United States army and the Thai government over seven years on volunteers - all HIV-negative men and women aged between 18 and 30 - in some of Thailand's most badly-affected regions.
Half of the volunteers were given the vaccine, while the other half were given a placebo - and all were given counselling on HIV/Aids prevention.
Participants were tested for HIV infection every six months for three years.
The results found that the chances of catching HIV were 31.2% less for those who had taken the vaccine - with 74 people who did not get the vaccine infected and 51 of the vaccinated group infected.