What are the situational and behavioral factors associated with condomless anal sex without pre-exposure prophylaxis in MSM?

International audienceObjective: 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),