HIV pre-exposure prophylaxis use with casual partners among men who have sex with men in Switzerland: testing an extended information-motivation-behavioral skills model.

Pre-exposure prophylaxis (PrEP) is an effective medical option for HIV prevention. This study aimed to examine PrEP uptake among men having sex with men (MSM) in Switzerland and to develop and test a theoretical model explaining PrEP use. We used an anonymous self-administered online questionnaire to collect data. In 2022, we recruited a convenience sample of 743 HIV-negative MSM who had had anal sex with casual partners 12 months prior to the survey. Approximately one-third of the participants used PrEP with casual partners. We used structural equation modeling to test a theoretical model of PrEP use based on an extended information-motivation-behavioral skills model (IMB model). The dependent variable measured how often MSM used PrEP with casual partners in the past year using a 7-point Likert scale. PrEP use was positively associated with intention to use PrEP (β = 0.51) and PrEP self-efficacy (β = 0.10). The intention to use condoms (β = -0.26) and the subjective HIV risk perception (β = -0.14) were negatively associated with PrEP use. The extended IMB model appeared suitable for explaining the frequency of PrEP use with casual partners (χ2(44) = 103.11, CFI = 0.98, RMSEA = 0.04, SRMR = 0.04, R2 = 0.49). The theoretical model provides valuable insights for prevention to further promote PrEP use among eligible MSM.