Emilio Emini, a bear of a man, spreads his arms wide and slaps one hand on either side of a 20-ton globe that rotates in a fountain in front of the Merck Research Laboratories in West Point, PA. Etched onto the globe are the seven continents, with stars marking the 10 satellite Merck research labs. "You can stop it," says Emini, muscling the globe to a halt. He then rotates it himself, showing off the stars in the United States, Canada, Europe and Japan; Africa sinks into the water and then reemerges.

Emini, who headed the Merck R&D team that in 1996 brought to market what has become a bestselling "protease inhibitor" drug against HIV, now runs the company's large AIDS vaccine research project. The effort's unprecedented scope and analytical rigor have invigorated the world of research aimed at shackling HIV with a vaccine, which could ultimately provide a far more powerful weapon against AIDS than drugs. While cocktails of anti-HIV drugs have lengthened many lives, no one has been cured, and patients must take several different kinds of pills, on a strict schedule, several times each day. The drugs also are costly, toxic, tricky to prescribe and, if improperly used, can lead to drug-resistant strains of HIV. Compare that to a vaccine, which after a few shots could protect someone from AIDS for years or decades.