title: HIV transmission among men who have sex with men due to condom failure.
abstract: BACKGROUND
  Despite preventive efforts, HIV incidence remains high among men who have sex with men (MSM) in industrialized countries. Condoms are an important element in prevention but, given the high frequency of condom use and their imperfect effectiveness, a substantial number and proportion of HIV transmissions may occur despite condoms. We developed a model to examine this hypothesis.
  
  
  METHODS
  We used estimates of annual prevalent and incident HIV infections for MSM in Ontario. For HIV-negative men, we applied frequencies of sexual episodes and per-contact HIV transmission risks of receptive and insertive anal sex with and without a condom and oral sex without a condom. We factored in the proportion of HIV-infected partners receiving antiretroviral therapy and its impact in reducing transmissibility. We used Monte-Carlo simulation to determine the plausible range for the proportion of HIV transmissions for each sexual practice.
  
  
  RESULTS
  Among Ontario MSM in 2009, an estimated 92,963 HIV-negative men had 1,184,343 episodes of anal sex with a condom and 117,133 anal sex acts without a condom with an HIV-positive partner. Of the 693 new HIV infections, 51% were through anal sex with a condom, 33% anal sex without a condom and 16% oral sex. For anal sex with a condom, the 95% confidence limits were 17% and 77%.
  
  
  CONCLUSIONS
  The proportion of HIV infections related to condom failure appears substantial and higher than previously thought. That 51% of transmissions occur despite condom use may be conservative (i.e. low) since we used a relatively high estimate (87.1%) for condom effectiveness. If condom effectiveness were closer to 70%, a value estimated from a recent CDC study, the number and proportion of HIV transmissions occurring despite condom use would be much higher. Therefore, while condom use should continue to be promoted and enhanced, this alone is unlikely to stem the tide of HIV infection among MSM.
authors.affiliation: Ontario HIV Epidemiologic Monitoring Unit, Dalla Lana School of Public Health, University of Toronto, Toronto, Canada.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Remis
authors.affiliation: Centre de Recherche, CHU de Québec, Québec, Canada; Département de Médecine Sociale et Préventive, Faculté de médecine, Université Laval, Québec, Canada; Institut National de Santé Publique du Québec, Québec, Canada.
authors.forename: Michel
authors.initials: M
authors.lastname: Alary
authors.affiliation: Ontario HIV Epidemiologic Monitoring Unit, Dalla Lana School of Public Health, University of Toronto, Toronto, Canada.
authors.forename: Juan
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Medicine, University Health Network, University of Toronto, Toronto, Canada.
authors.forename: Rupert
authors.initials: R
authors.lastname: Kaul
authors.affiliation: Ontario HIV Epidemiologic Monitoring Unit, Dalla Lana School of Public Health, University of Toronto, Toronto, Canada.
authors.forename: Robert W H
authors.initials: RW
authors.lastname: Palmer
mesh_terms: D017280:Condoms / Q000592:standards*; D004868:Equipment Failure; D015658:HIV Infections / Q000453:epidemiology / Q000517:prevention & control / Q000635:transmission*; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D009864:Ontario / Q000453:epidemiology; D015995:Prevalence; D012307:Risk Factors; D021841:Safe Sex; D012725:Sexual Behavior