Results of a randomized, placebo-controlled trial – called CAPRISA 004 - have indicated that a vaginal microbicide gel containing the HIV drug tenofovir reduces the risk of infection with HIV for women using it by 39%. For women who used the gel during four out of the last five times they had had sex, the risk of HIV infection was reduced by 54%. The microbicide also had another important benefit, halving the risk of infection with genital herpes.

The study was conducted in South Africa and involved 889 HIV-negative women who were randomised to receive the tenofovir containing gel or a placebo. They were monitored for two and a half years. These results presented at AIDS 2010 in Vienna have generated excitement in the field. The challenge is now to mobilize funding for additional studies required on the gel. Equally important are debates around the implications of "antiretroviral (ARV)-based prevention".

Over the past few years, the HIV prevention research field has increasingly focused on the possibilities of ARV-based prevention. However, the use of ARV-containing compounds for prevention raises several questions about their safety, the potential for drug resistance, the need for scale-up of testing, and the implications for treatment options for those in trials who become HIV-positive. The role of HIV-positive people in shaping biomedical prevention research has therefore never been more important.

There are significant questions that remain to be answered about ARV-based prevention, and people living with HIV could contribute to addressing them: ethical issues around testing and making ARVs available for prevention when they are not accessible for treatment in many contexts; the potential for drug resistance, drug sharing and black markets; safety concerns; potential funding barriers and competition between prevention and treatment programmes.