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PrEP Does Not Promote Increased Sexual Risk Behavior among Gay Men


Using Truvada (tenofovir/emtricitabine) for pre-exposure prophylaxis (PrEP) to prevent HIV infection was not associated with an increase in sex without condoms and it appears to promote active engagement in risk reduction, according to a report in the December 18, 2013, edition of PLoS ONE.

The international iPrEx study -- which enrolled nearly 2500 at-risk men who have sex with men and a small number of transgender women in Brazil, Ecuador, Peru, South Africa, Thailand, and the U.S. -- showed that daily Truvada lowered the risk of HIV acquisition risk by 44% overall compared with placebo, and by more than 90% among participants who had blood drug levels indicating that they took it regularly.

Julia Marcus and Robert Grant from the Gladstone Institute of Virology and Immunology and colleagues aimed to determinewhether people who used PrEP in the study appeared to be having more risky sex. Self-reported sexual risk behavior decreased overall in iPrEx, but this may be affected by reporting bias, they noted as background. This analysis, therefore, looked at biomarkers of sexual risk behavior.

Sexual practices were assessed at study entry and then quarterly thereafter. At 12 weeks, participants were asked whether they thought they had been randomly assigned to Truvada or placebo and how effective they thought PrEP would be. Among participants with at least 1 follow-up assessment, sexual behavior, prevalence of syphilis, and HIV infection were compared according to perceived treatment assignment, actual treatment assignment, and perceived PrEP efficacy.


  • Overall, both acute HIV infection and syphilis incidence decreased during follow-up.
  • Participants who thought they were receiving Truvada reported receptive anal intercourse with more partners prior to starting PrEP compared with those who thought they were receiving placebo (12.8 vs 7.7, respectively).
  • Believing one had been assigned to take Truvada was not associated with an increase in receptive anal intercourse without a condom.
  • People who thought they were assigned to Truvada also did not report a decrease in sex without condoms after stopping their study drug.
  • In the placebo arm, there were trends toward lower HIV incidence among participants who believed they were receiving Truvada (incidence rate ratio [IRR] 0.8; p=0.26) and who thought Truvada was highly effective (IRR 0.5; p=0.12).
  • Younger men, transgender women, and participants who reported depression were more likely to have anal sex without condoms.

"There was no evidence of sexual risk compensation in iPrEx," the study authors concluded. "Participants believing they were receiving [Truvada] had more partners prior to initiating drug, suggesting that risk behavior was not a consequence of PrEP use."

Thislack of "risk compensation" -- or increased risk behavior if people think they are protected -- is "largely consistent with other HIV prevention studies of PrEP, male circumcision, vaccines, and PEP [post-exposure prophylaxis]," they noted in their discussion. They added that in actual practice (rather than a controlled trial) people would know they are receiving the active drug and those who seek PrEP are likely to believe it is effective.

"One-quarter of participants had never been tested for HIV prior to their iPrEx screening visit and reported safer sexual behavior during study follow-up than those who had previously tested," the researchers wrote. "Prior studies conducted among [men who have sex with men] and adults in developing countries have found decreases in sexual risk behavior associated with HIV testing. That effect has been more pronounced among individuals testing positive, but the benefit of testing may be increased for HIV negative individuals who are testing periodically, as would occur in PrEP programs."

"The regular testing that accompanies PrEP use, as well as the act of taking PrEP itself, could increase contemplation of HIV risk as manageable rather than inevitable and motivate other risk-reduction strategies," they continued. "Indeed, PrEP may increase self-efficacy regarding condom use and reduce fatalism about HIV by providing a daily opportunity for users to manage their own risk."

"Our results suggest that HIV prevention strategies such as Truvada don’t result in risk compensation because they provide an opportunity for participants to actively engage in and reduce their risk of HIV infection," iPrEx principle investigator Grant said in a UCSF press release. "Engagement, which also includes counseling, provision of condoms and management of other sexually transmitted infections, leads to motivation, which comes at a time when motivation for preventing new HIV infections is vital to curbing the spread of this worldwide epidemic."



JL Marcus,
DV Glidden, K Mayer, R Grant, et al. No Evidence of Sexual Risk Compensation in the iPrEx Trial of Daily Oral HIV Preexposure Prophylaxis. PLoS ONE 8(12): e81997. December 18, 2013.

Other Source

University of California at San Francisco. No Link between HIV-Prevention Pill Truvada and Increased Sexual Risk Behavior, Study Finds. Press release. December 18, 2013.