The SwissPrEPared study was approved by all Swiss cantonal ethical committees (lead canton: Zurich, Switzerland, registration number: 2018–02015) and was registered with Clinical Trials.gov (NCT03893188). Written informed consent was obtained from all participants included in this study. BH, JSF, AC, and MS conceptualised and designed the study. BH, AF, CC, and JSF analysed and discussed the data, and wrote the Correspondence. PJL-M and PUA collected samples, enrolled patients, and collected and managed clinical data. All authors read, revised, and approved this Correspondence. This study was supported by the Federal Office of Public Health (approval number 19.022422], Merck Sharp & Dohme, and the Swiss HIV Cohort Study (grant number SHCS_281). BH, AF, and CC were supported by the Federal Office of Public Health (approval number 19.022422). The funding organisations had no role in the design and conduct of the study, the collection, management, analysis, or interpretation of the data, or in the preparation, review, or approval of the manuscript. JSF received research grants unrelated to the submitted work from Merck Sharp & Dohme, Gilead Sciences, and ViiV Healthcare. JSF and BH received advisory fees from the Swiss Federal Commission for issues relating to sexually transmitted infections. BH's institution received research and travel grants from ViiV Healthcare, Merck Sharp and Dohme, and Gilead Sciences. BH received advisory fees from Gilead Sciences and ViiV Healthcare. The other authors declare no competing interests.