Since 1981, when it was first observed that young gay men in Los Angeles were becoming ill as a result of what was later called Acquired Immune Deficiency Syndrome, or Aids, scientists have made strenuous efforts to treat and prevent the disease. By 1987 significant progress appeared to have been made, with the licensing of the first Aids drug, AZT, and approval in the US for the first human trial of a vaccine. But it was not until 1995 that a new type of Aids drug was approved, opening the way for the three-drug combination antiretroviral therapy, which now keeps people with HIV well. Experts believed science would banish Aids, but all attempts to invent a vaccine have failed. One candidate, Aidsvax, completed large human trials in Thailand in 2003, but failed to protect against infection.