Exciting news emerged from a recent clinical trial in Africa, demonstrating the effectiveness of a biannual injection of the antiviral drug lenacapavir in providing complete protection against H.I.V. infection in young women. The trial, called Purpose 1, compared the injection with daily pills and was halted early due to the injection's superior protection. Gilead Sciences, the manufacturer, plans to make the drug available at accessible prices in low-income countries. This breakthrough offers hope for better H.I.V. prevention, particularly for young African women, and highlights the importance of addressing access challenges to ensure widespread availability.