Merck & Co. had the Seattle confab buzzing by announcing a year-long safety test of its HIV vaccine in a small group of negative volunteers. In monkeys, the high-profile vax cut viral load sharply and slowed disease. If successful, the Merck vaccine not only would prove a boon for prevention but would also be fast-tracked for the treatment of HIVers.

The vaccine uses a "prime-boost" strategy -- two vax constructs are administered, one after the other. The primer takes advantage of "naked DNA" technology, as tiny fragments of HIV are injected directly into the muscle. The "boost" consists of an adenovirus "vector" -- a safe envelope into which HIV's gag protein is inserted.

The two-pronged strategy is designed to augment the killer-T cell ("CTL") attack against the virus. Response rates have been encouraging -- from 50 to 70 percent. Merck med head Emilio Emini says he plans to launch a study in some 600 HIVers in the near future.