title: Sexual behaviour of heterosexual men and women receiving antiretroviral pre-exposure prophylaxis for HIV prevention: a longitudinal analysis.
abstract: BACKGROUND
  Scarce data are available to assess sexual behaviour of individuals using antiretroviral pre-exposure prophylaxis for HIV prevention. Increased sexual risk taking by individuals using effective HIV prevention strategies, like pre-exposure prophylaxis, could offset the benefits of HIV prevention. We studied whether the use of pre-exposure prophylaxis in HIV-uninfected men and women in HIV-serodiscordant couples was associated with increased sexual risk behaviour.
  
  
  METHODS
  We undertook a longitudinal analysis of data from the Partners PrEP Study, a double-blind, randomised, placebo-controlled trial of daily oral pre-exposure prophylaxis among HIV-uninfected partners of heterosexual HIV-serodiscordant couples (n=3163, ≥18 years of age). Efficacy for HIV prevention was publicly reported in July 2011, and participants continued monthly follow-up thereafter. We used regression analyses to compare the frequency of sex-unprotected by a condom-during the 12 months after compared with the 12 months before July 2011, to assess whether knowledge of pre-exposure prophylaxis efficacy for HIV prevention caused increased sexual risk behaviour.
  
  
  RESULTS
  We analysed 56 132 person-months from 3024 HIV-uninfected individuals (64% male). The average frequency of unprotected sex with the HIV-infected study partner was 59 per 100 person-months before unmasking versus 53 after unmasking; we recorded no immediate change (p=0·66) or change over time (p=0·25) after July, 2011. We identified a significant increase in unprotected sex with outside partners after July, 2011, but the effect was small (average of 6·8 unprotected sex acts per year vs 6·2 acts in a predicted counterfactual scenario had patients remained masked, p=0·04). Compared with before July, 2011, we noted no significant increase in incident sexually transmitted infections or pregnancy after July, 2011.
  
  
  CONCLUSIONS
  Pre-exposure prophylaxis, provided as part of a comprehensive prevention package, might not result in substantial changes in risk-taking sexual behaviour by heterosexual couples.
  
  
  BACKGROUND
  The Bill & Melinda Gates Foundation and the US National Institute of Mental Health.
authors.affiliation: Department of Epidemiology, University of Washington, Seattle, WA, USA; Department of Disease Control and Environmental Health, Makerere University, Kampala, Uganda.
authors.forename: Kenneth K
authors.initials: KK
authors.lastname: Mugwanya
authors.forename: Deborah
authors.initials: D
authors.lastname: Donnell
authors.forename: Connie
authors.initials: C
authors.lastname: Celum
authors.forename: Katherine K
authors.initials: KK
authors.lastname: Thomas
authors.forename: Patrick
authors.initials: P
authors.lastname: Ndase
authors.forename: Nelly
authors.initials: N
authors.lastname: Mugo
authors.forename: Elly
authors.initials: E
authors.lastname: Katabira
authors.forename: Kenneth
authors.initials: K
authors.lastname: Ngure
authors.forename: Jared M
authors.initials: JM
authors.lastname: Baeten
mesh_terms: D000328:Adult; D044966:Anti-Retroviral Agents / Q000008:administration & dosage*; D004311:Double-Blind Method; D005260:Female; D015658:HIV Infections / Q000517:prevention & control* / Q000523:psychology*; D015497:HIV-1 / Q000302:isolation & purification*; D020010:Heterosexuality / Q000523:psychology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D012309:Risk-Taking; D012725:Sexual Behavior / Q000187:drug effects* / Q000523:psychology*
chemical_list: D044966:Anti-Retroviral Agents