WITH ALL THAT is now known about the deadly AIDS virus, scientists still lack the ability to cure the disease or prevent it through a vaccine. Efforts to accomplish both have been under way for many years. Those efforts have been hobbled by the complex and changeable nature of the human immunodeficiency virus (HIV) and by financial limitations and moral and ethical concerns.

Most experts think that a vaccine will one day eliminate AIDS just as other vaccines have done away with the deadly diseases of the recent past—smallpox, polio, and measles, to name a few. With that day still years away, the biggest hope for the present is finding a way to control or manage the disease much as people with diabetes or asthma manage their chronic conditions. Progress on this front has been substantial...