Behavioral impact, acceptability, and HIV incidence among homosexual men with access to postexposure chemoprophylaxis for HIV

J Acquir Immune Defic Syndr. 2004 Apr 15;35(5):519-25. doi: 10.1097/00126334-200404150-00010.


Background: Little is known about the behavioral impact, acceptability, and incidence of HIV infection in persons with easy access to post-sexual exposure prophylaxis (PEP) to prevent HIV.

Methods: Participants were recruited from a well-characterized, high-risk HIV seronegative homosexual male cohort in Rio de Janeiro, Brazil, given a 4-day supply of zidovudine and lamivudine, and instructed to begin PEP immediately after an eligible exposure. For eligible exposures, an additional 24-day supply was provided. Reported behavior, PEP utilization, adverse events, and incident HIV infection were the main study outcomes. The observed and expected incidences of HIV infection were compared.

Results: Two hundred subjects were enrolled and followed for a median of 24.2 months. The median age was 28 years. PEP was initiated 109 times by 68 participants (34.0%). In comparison to reported behavior at baseline, reported high-risk sexual activities on average declined over time for both PEP and non-PEP users. There were no serious drug-related adverse events. There were 11 HIV seroconversions, 10 among non-PEP users and 1 that was a PEP failure. The overall seroincidence was 2.9 per 100 person-years (95% CI = 1.4, 5.1). The expected number of new HIV infections and corresponding expected seroincidence based on the risk profile were 11.8 and 3.1, respectively (P > 0.97). The most commonly reported reasons for not initiating PEP among seroconverters were sex with a steady partner and not considering the exposure to be of sufficiently high risk to warrant PEP.

Conclusion: PEP was safe and did not appear to be associated with increases in reported high-risk behavior in our cohort. Ready access to PEP did not appear to substantially affect HIV transmission, suggesting a limited public health impact of this intervention.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Anti-HIV Agents / therapeutic use*
  • Brazil / epidemiology
  • Chemoprevention
  • Cohort Studies
  • HIV Infections / immunology
  • HIV Infections / prevention & control*
  • HIV Infections / psychology
  • HIV Seropositivity
  • Homosexuality, Male
  • Humans
  • Lamivudine / therapeutic use*
  • Male
  • Patient Acceptance of Health Care
  • Sexual Behavior
  • Surveys and Questionnaires
  • Zidovudine / therapeutic use*


  • Anti-HIV Agents
  • Lamivudine
  • Zidovudine