"A new AIDS vaccine tested on more than 16,000 volunteers in Thailand has protected a significant minority against infection, the first time any vaccine against the disease has even partly succeeded in a clinical trial.
"Scientists said they were delighted but puzzled by the result. The vaccine a combination of two genetically engineered vaccines, neither of which had worked before in humans protected too few people to be declared an unqualified success. And the researchers do not know why it worked.
"I don't want to use a word like breakthrough,' but I don't think there's any doubt that this is a very important result, said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, which is one of the trial's backers."