HIV prevention may only require two injections per year

A clinical trial reports no infections among adolescent girls and young women getting the shots

A girl in a school uniform exits a mobile clinic for HIV counseling and prevention in South Africa.

A student leaves a mobile clinic after getting an HIV test in Kwazulu Natal, South Africa. Adolescent girls and young women in sub-Saharan Africa are at high risk of HIV.

STEPHANE DE SAKUTIN/AFP/Getty Images

Zero: That’s the number of new HIV infections among young women and adolescent girls who took a twice-yearly preventive medicine.