By The Editors

Researchers in South Africa announced this week the development of a vaginal microbicidal gel that in clinical trials has sharply reduced the possibility of women contracting H.I.V. from infected partners. The gel, which contains an antiretroviral medication widely used to treat AIDS, cut the odds of women in the study being infected by more than half – 54 percent, researchers said.

The news provoked a burst of optimism among scientists and AIDS researchers around the world who have been struggling for nearly three decades to develop medicines that will significantly reduce the damage the AIDS scourge can do. Dr. Bruce Walker, a professor at Harvard Medical School who was not involved in the study but was present at a small gathering of scientists in Durban, South Africa when the researchers reported their findings, said “This is the first time that there’s been a tool that women can use to protect themselves from becoming infected. It’s a game changer.”