For First Time, AIDS Vaccine Shows Some Succes

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.

Although the difference was small, Dr. Kim said it was statistically significant and meant the vaccine was 31.2 percent effective.

Whatever the vaccine does, he said, it does not seem to mimic the defenses of the rare individuals known to AIDS doctors as "long-term nonprogressors," who do not get sick even though they are infected.