After 10 years of research, experts are in a better position to judge the future. The consensus: a fully effective AIDS vaccine is a long way off. "There are people who will tell you we will never have a vaccine—I can't say those people are wrong," says Columbia's Hammer. But "you shouldn't be in this business if you don't have some degree of optimism based on the science. The world needs an AIDS vaccine. To give up now is selling the science short."