Pre-exposure prophylaxis (PrEP) versus treatment-as-prevention (TasP) for the control of HIV: Where does the balance lie?

* South African Centre for Epidemiological Modelling and Analysis, Stellenbosch, South Africa † Joint United Nations Programme on HIV/AIDS (UNAIDS), Geneva, Switzerland Correspondence to [email protected] Abstract Anti-retroviral drugs can reduce the infectiousness of people living with HIV by about 96%—‘treatment as prevention’ or TasP—and can reduce the risk of being infected by an HIV positive person by about 70%—‘pre-exposure prophylaxis’ or PrEP—raising the prospect of using anti-retroviral drugs to stop the epidemic of HIV. The question as to which is more effective, more affordable and more cost effective, and under what conditions, continues to be debated in the scientific literature. Here we compare TasP and PreP in order to determine the conditions under which each strategy is favourable. This analysis suggests that where the incidence of HIV is less than 5% or the risk-reduction under PrEP is less than 50%, TasP is favoured over PrEP; otherwise PrEP is favoured over TasP. The potential for using PreP should therefore be restricted to those among whom the annual incidence of HIV is greater than 5% and TasP reduces transmission by more than 50%. PreP should be considered for commercial sex workers, young women aged about 20 to 25 years, men-who-have-sex with men, or intravenous drug users, but only where the incidence of HIV is high.