They plan an additional 18-month study, starting next year, to explore the drug's long-term effectiveness and safety, as well as risk behavior and pill-taking practices.

WSJ: Daily Pill Slashes Risk of HIV Infection in Study

This may be because some people were erroneously put on the drugs, or because years of drug therapy healed heart damage, or simply because taking people off the pills motivates them to clean up their behavior.

FORBES: On The Cover/Top Stories