accine that can prevent people who are exposed to H.I.V. from acquiring the infection. But the same variability that allows H.I.V. to elude drugs also makes it a very difficult to trap the virus into a vaccine. So the challenges of AIDS research now lie along two lines. First, new drugs must be devised to keep people who are already infected with H.I.V. from getting sick, drugs that are safer and easier to take than the older ones and active against virus that has grown resistant to the older drugs. Second, H.I.V. must be stopped from passing from person to person and causing new infections. Until an effective vaccine is developed the best methods of preventing new infections seem to be relatively old- fashioned ones: educating people about the disease, encouraging those who may be infected to get tested, and developing effective ways of discouraging illicit drug use and encouraging condom use to prevent sexually transmitted infections....
