The search for an AIDS vaccine is mocked as monkey business by such experts as Robert Gallo, who say it’ll never happen. But on the heels of President Clinton’s call in May for a national push to develop one within 10 years came word that two vaccinated chimps have fought off repeated exposures to the virus. The primates’ sustained immune response is widely viewed as a breakthrough in a field littered with past promises that delivered only short-term protection.

The vaccine was made from an adenovirus (a cause of colds in humans) genetically engineered to incorporate gp160, an HIV-specific gene. After being vaccinated with a series of nasal sprays and a booster shot, the chimps responded to the HIV proteins by making antibodies and white blood cells programmed to attack HIV. At presstime, they remained HIV-free - close to a year after inoculation.