Nonhuman primate data have suggested that the administration of ARV medication before or after retroviral exposure can protect against the establishment of chronic infection.
Over the past two decades, observational studies have demonstrated the safety of ARV agents for postexposure prophylaxis and more recent efficacy studies have demonstrated that tenofovir with or without emtricitabine can protect against HIV when used as preexposure prophylaxis (PrEP). Efficacy studies have been conducted in diverse populations, including men and transgender women who have sex with men, young African heterosexuals, and injection drug users. Three studies in African women evaluating oral and topical tenofovir-based regimens did not demonstrate efficacy, in large part because of suboptimal medication adherence. Further research is underway to determine the optimal ways to provide chemoprophylaxis, the optimal medications, and dosing regimens.
PrEP can be effective in decreasing HIV transmission to at-risk uninfected persons, but further research is needed to determine the optimal modes of delivery.