The success of a promising HIV prevention intervention in sub-Saharan Africa — the region with the highest burden of HIV — will hinge more on the social than the scientific. Researchers and advocates will have to strike a balance in how they market and roll out pre-exposure prophylaxis (PrEP). They have to ensure that it reaches stigmatized populations with high HIV transmission rates, such as MSM and sex workers. But they must ensure it is not perceived as exclusively a treatment for marginalized groups, which will lower its appeal both within those communities but also to other people who could benefit from it. Read more.