What are the situational and behavioral factors associated with condomless anal sex without PrEP in men who have sex with men? Results from the ANRS-IPERGAY trial.

OBJECTIVE: This study aimed to identify situational and behavioral factors associated with condomless anal sex without on-demand PrEP in the open-label extension (OLE) study of the ANRS-IPERGAY trial. METHODS: Univariable and multivariable modified Poisson regressions with a generalized estimating equation (GEE) were used. The attributable risk percentage for each explanatory variable and for condomless anal sex without PrEP was calculated. RESULTS: In the OLE, 19% of anal intercourses were unprotected (i.e., no PrEP or condom). Of these, 85% were attributable to sexual intercourse with main partners and 47% with HIV-negative partners. The following factors were positively associated with condomless anal sex without PrEP: a depressive episode in the previous 12 months (aR [95% CI], p-value: 1.49 [1.02;2.17], 0.039), a higher number of sexual intercourses during the previous 4 weeks (1.01 [1.002;1.02], 0.014), and sexual intercourses under the influence of alcohol (1.45 [1.10;1.92], 0.008). By contrast, condomless anal sex without PrEP was less frequent during sexual intercourses with known casual, unknown casual and multiple partners (0.20 [0.14;0.30], < 0.001; 0.10 [0.05;0.20], < 0.001; 0.11 [0.05;0.29], < 0.001, respectively), as well as with HIV+ partners with an undetectable viral load (VL) and HIV+ partners with a detectable/unknown VL or unknown serology status (0.57 [0.38;0.86], 0.007; 0.52 [0.32;0.87],0.012, respectively). CONCLUSIONS: Choosing to have condomless anal sex without PrEP depends primarily on the sexual partner's characteristics (level of intimacy, serological status). This reflects a form of rationality in HIV risk management. However, our results raise questions about the true efficacy of managing HIV risk using this approach.