An experimental HIV vaccine has cut the risk of infection by nearly a third in a major trial, researchers say. The vaccine – a combination of two earlier experimental vaccines – was given to 16,000 people in a joint trial by the Thai government and the US military. It reduced by 31 per cent the volunteers' risk of contracting HIV, the virus that leads to AIDS. The researchers said the results give fresh hope that a safe and effective vaccine may yet be possible. <br/>