Abstract
ObjectivePreexposure prophylaxis (PrEP) with emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) reduced HIV acquisition in the iPrEx trial among men who have sex with men and transgender women. Self-reported sexual risk behavior decreased overall, but may be affected by reporting bias. We evaluated potential risk compensation using biomarkers of sexual risk behavior.Design and methodsSexual practices were assessed at baseline and quarterly thereafter; perceived treatment assignment and PrEP efficacy beliefs were assessed at 12 weeks. Among participants with ≥1 follow-up behavioral assessment, sexual behavior, syphilis, and HIV infection were compared by perceived treatment assignment, actual treatment assignment, and perceived PrEP efficacy.ResultsOverall, acute HIV infection and syphilis decreased during follow-up. Compared with participants believing they were receiving placebo, participants believing they were receiving FTC/TDF reported more receptive anal intercourse partners prior to initiating drug (12.8 vs. 7.7, P = 0.04). Belief in receiving FTC/TDF was not associated with an increase in receptive anal intercourse with no condom (ncRAI) from baseline through follow-up (risk ratio [RR] 0.9, 95% confidence interval [CI]: 0.6–1.4; P = 0.75), nor with a decrease after stopping study drug (RR 0.8, 95% CI: 0.5–1.3; P = 0.46). In the placebo arm, there were trends toward lower HIV incidence among participants believing they were receiving FTC/TDF (incidence rate ratio [IRR] 0.8, 95% CI: 0.4–1.8; P = 0.26) and also believing it was highly effective (IRR 0.5, 95% CI: 0.1–1.7; P = 0.12).ConclusionsThere was no evidence of sexual risk compensation in iPrEx. Participants believing they were receiving FTC/TDF had more partners prior to initiating drug, suggesting that risk behavior was not a consequence of PrEP use.
Highlights
Belief in receiving FTC/TDF was not associated with an increase in receptive anal intercourse with no condom from baseline through follow-up, nor with a decrease after stopping study drug (RR 0.8, 95% CI: 0.5–1.3; P = 0.46)
Like other prevention strategies – including circumcision, condom use, and human immunodeficiency virus (HIV) testing – excitement about preexposure prophylaxis (PrEP) has been tempered by concerns about potential increases in sexual risk behavior among users, [11,12] an effect defined as ‘‘risk compensation.’’ [13] According to risk compensation theory, individuals adjust their behavior in response to changes in their perceived level of risk. [13,14] This theory has been used as an explanation for why population-level benefits of seatbelt use have not been observed, [15] sunscreen use has been associated with an increased risk of melanoma, [16] and condom promotion has had a limited population-level impact on HIV in communities with generalized epidemics
[15] Risk compensation has been linked to increases in sexual risk behavior coinciding with the introduction of combination antiretroviral therapy, an effect called ‘‘treatment optimism.’’ [17] PrEP optimism could result in increased risk behavior that could potentially reduce its protection against HIV acquisition. [18,19]
Summary
Despite decades of prevention efforts, human immunodeficiency virus (HIV) infection is a global pandemic, with 2.5 million people newly infected in 2011 [1] and men who have sex with men (MSM) disproportionately affected worldwide. [2,3] As behavioral interventions have not been sufficient to end the epidemic, research has included biomedical interventions. [4] In the primary analysis of the iPrEx randomized controlled trial (RCT), preexposure prophylaxis (PrEP) with once-daily oral emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) reduced the risk of HIV acquisition by 44% among HIV-uninfected MSM and transgender women compared with placebo, and by 92% among participants with detectable drug levels; a subsequent modeling study estimated a 96–99% risk reduction among those with drug concentrations commensurate with daily dosing. [5,6] two interventions in African women – the oral and topical tenofovir arms of the VOICE study and the FEM-PrEP [7] trial of FTC/TDF – were closed early for futility, and the FTC/TDF arm of the VOICE study later showed no effect, [8] the Partners PrEP study in heterosexual serodiscordant couples [9] and the CDC PrEP trial in heterosexual men and women [10] found oral FTC/ TDF to be highly effective.Like other prevention strategies – including circumcision, condom use, and HIV testing – excitement about PrEP has been tempered by concerns about potential increases in sexual risk behavior among users, [11,12] an effect defined as ‘‘risk compensation.’’ [13] According to risk compensation theory, individuals adjust their behavior in response to changes in their perceived level of risk. [13,14] This theory has been used as an explanation for why population-level benefits of seatbelt use have not been observed, [15] sunscreen use has been associated with an increased risk of melanoma, [16] and condom promotion has had a limited population-level impact on HIV in communities with generalized epidemics. [15] Risk compensation has been linked to increases in sexual risk behavior coinciding with the introduction of combination antiretroviral therapy, an effect called ‘‘treatment optimism.’’ [17] PrEP optimism could result in increased risk behavior that could potentially reduce its protection against HIV acquisition. [18,19].Empirically, previous studies of biomedical HIV-prevention interventions have found mixed evidence of risk compensation. Like other prevention strategies – including circumcision, condom use, and HIV testing – excitement about PrEP has been tempered by concerns about potential increases in sexual risk behavior among users, [11,12] an effect defined as ‘‘risk compensation.’’ [13] According to risk compensation theory, individuals adjust their behavior in response to changes in their perceived level of risk. Behavior in the trial context may differ from behavior during subsequent implementation, when there is no longer the possibility that the user is receiving a placebo To address these concerns, we conducted an analysis using biomarkers of sexual risk behavior and focusing on the group of participants who believed they were receiving the active drug and that it was effective. We aimed to describe trends in sexual behavior during study follow-up and after stopping study drug; to describe trends in the acquisition of HIV and syphilis; and to determine whether participants who believed they were receiving FTC/TDF and that it was highly effective had increased sexual risk behavior or increased risk of HIV or syphilis acquisition compared with participants who believed they were receiving placebo
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