WASHINGTON (Reuters) - More than 3,000 people who volunteered to receive an experimental Merck and Co. AIDS vaccine are being told to come back and get extra tests because the jab may itself raise the risk of infection.Researchers stress that they do not yet have enough information to say whether those who got the shot indeed are more susceptible to infection with HIV. But they said initial information from the trial, which was stopped suddenly last month, is worrisome.
