Pre-exposure prophylaxis sorting among men who have sex with men.

Factors such as race, masculinity, and sexually transmitted infections have been documented to influence partner selection in men who have sex with men (MSM). Pre-exposure prophylaxis (PrEP) has received mixed evaluations as a responsible step in HIV prevention and as an enabler of risker sexual practices. PrEP may consequently serve as an additional factor in partner choice. We examine the role that PrEP use and "promiscuity" play in affiliation and dating decisions by men who have sex with men with different HIV and PrEP stati. We invited 450 MSM across the United States from a smartphone geo-locating sex application to complete a survey of which 339 successfully finished the task. The survey contained vignettes of fictional men who were promiscuous or monogamous and either taking PrEP or not. Participants provided responses on whether to affiliate with these characters in three social domains: as friends, dates, or sex partners. Neither PrEP nor promiscuity influenced friendship choices. There was a preference for dating monogamous characters. Critically, PrEP influenced sexual affiliations for HIV negative individuals who showed a preference for PrEP-using characters. The pattern of results provides quantitative evidence for PrEP-based sexual sorting aimed at reducing risk of HIV transmission.