Incidence of sexually transmitted infections and association with behavioural factors: Time-to-event analysis of a large pre-exposure prophylaxis (PrEP) cohort.

Hovaguimian, Frédérique; Kouyos, Roger D; Kusejko, Katharina; Schmidt, Axel J; Tarr, Philip E; Bernasconi, Enos; Braun, Dominique L; Calmy, Alexandra; Notter, Julia; Stoeckle, Marcel; Surial, Bernard; Christinet, Vanessa; Darling, Katharine E A; Depmeier, Carsten; Läuchli, Severin; Reinacher, Matthias; Rasi, Manuela; Nicca, Dunja; Bruggmann, Philip; Haerry, David; ... (2024). Incidence of sexually transmitted infections and association with behavioural factors: Time-to-event analysis of a large pre-exposure prophylaxis (PrEP) cohort. HIV medicine, 25(1), pp. 117-128. Wiley 10.1111/hiv.13543

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Our objective was to obtain long-term data on the incidence of sexually transmitted infections (STIs) and their association with behavioural factors after widespread pre-exposure prophylaxis (PrEP) implementation.


This was a time-to-event analysis of a national PrEP cohort in Switzerland (SwissPrEPared study). Participants were people without HIV interested in taking PrEP with at least two STI screening visits. Primary outcomes were incidence rate of gonorrhoea, chlamydia, and syphilis. The association between behavioural factors and STI diagnosis was expressed using hazard ratios. We adjusted for testing frequency and calendar year.


This analysis included 3907 participants enrolled between April 2019 and April 2022, yielding 3815.7 person-years of follow-up for gonorrhoea (15 134 screenings), 3802.5 for chlamydia (15 141 screenings), and 3858.6 for syphilis (15 001 screenings). The median age was 39 years (interquartile range [IQR] 32-47), 93.8% (n = 3664) identified as men who have sex with men (MSM). The incidence was 22.8 (95% confidence interval [CI] 21.3-24.4) per 100 person-years for gonorrhoea, 26.3 (95% CI 24.7-28.0) for chlamydia, and 4.4 (95% CI 3.8-5.1) for syphilis. Yearly incidence rates decreased between 2019 (all bacterial STIs: 81.6; 95% CI 59.1-109.9) and 2022 (all bacterial STIs: 49.8; 95% CI 44.6-55.3). Participants reporting chemsex substance use were at higher risk of incident STIs, as were those reporting multiple sexual partners. Younger age was associated with a higher risk of gonorrhoea and chlamydia.


Incidence rates of bacterial STIs decreased over time. Young MSM, those with multiple partners, and those using chemsex substances were at increased risk of STIs.

Item Type:

Journal Article (Original Article)


04 Faculty of Medicine > Department of Haematology, Oncology, Infectious Diseases, Laboratory Medicine and Hospital Pharmacy (DOLS) > Clinic of Infectiology
04 Faculty of Medicine > Pre-clinic Human Medicine > Institute of Social and Preventive Medicine (ISPM)

UniBE Contributor:

Surial, Bernard, Low, Nicola


600 Technology > 610 Medicine & health
300 Social sciences, sociology & anthropology > 360 Social problems & social services






[191] Swiss Federal Office of Public Health = Bundesamt für Gesundheit ; [4] Swiss National Science Foundation




Pubmed Import

Date Deposited:

02 Oct 2023 15:14

Last Modified:

04 Jan 2024 12:37

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Uncontrolled Keywords:

behavioural factors incidence rate pre-exposure prophylaxis sexually transmitted infections




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