For the vaccine to fulfill its promise, the next five years may be just as crucial as the last 20. Merck plans to bring it to market by 2007. The pharmaceutical giant will need to conduct more tests to ensure ironclad safety. It will also have to formulate a version of the vaccine that can ward off multiple strains of HPV. (The version revealed last week protects against only one type.) It will have to persuade men as well as women to get immunized. And it will have to do it all without pushing the price of the vaccine past the limits of developing countries, where the need is greatest since screening isn’t as common. “I don’t want to throw a wet blanket on the enthusiasm,” says gynecologic oncologist Charles Levenback, “but women still need to get Pap smears.” For those who can’t, though, the vaccine could be a lifesaver.