PLOS One | January 2017
Objectives: Risk compensation (RC) could reduce or offset the biological prevention benefits of HIV preexposure prophylaxis (PrEP) among those at substantial risk of infection, including men who have sex with men (MSM). We investigated the potential extent and causal mechanism through which RC could impact HIV transmission at the population and individual levels.
Methods: Using a stochastic network-based mathematical model of HIV transmission dynamics among MSM in the United States, we stimulated RC as a reduction in the probability of condom use after initiating PrEP, with heterogeneity by PrEP adherence profiles and partnership type in which RC occurred. Outcomes were changes to population-level HIV incidence and individual level acquisition risk.
Results: When RC was limited to MSM highly/moderately adherent to PrEP, 100% RC (full replacement of condoms) results in a 2% relative in incidence compared to no RC, but an 8% relative increase in infection risk for MSM on PrEP. This resulted from confounding by indication: RC increased the number of MSM indicated for PrEP as a function of more condomless anal intercourse among men otherwise indicated for PrEP; this led to an increase PrEP uptake and subsequent decline in incidence.
Conclusion: RC is unlikely to decrease prevention impact of PrEP and in some cases RC may be counterintuitively beneficial at the population level. This deepened on PrEP uptake scaling with behavioral indications. Due to the increased acquisition risk associated with RC, however clinicians should continue to support PrEP as a supplement rather than replacement of condoms.