Questioning risk compensation:pre-exposure prophylaxis (PrEP) and sexually transmitted infections among men who have sex with men, capital region of Denmark, 2019 to 2022

Background: Pre-exposure prophylaxis (PrEP) effectively prevents HIV, but its association with sexuallytransmitted infections (STIs) has raised concerns aboutrisk compensation, potentially impacting the expansion of PrEP programmes. Aim: We examined the relationship between PrEP and the incidence of chlamydia,gonorrhoea and syphilis. Methods: In this prospective cohort study, we compared STI rates before andafter PrEP initiation among users in the capital regionof Denmark (2019–2022), calculating incidence rateratios adjusted for age and testing frequency (aIRR).To pinpoint when increases began, we plotted weeklySTI rates, adjusting the timeline to correspond withPrEP initiation. Results: The study included 1,326 PrEPusers with a median age of 35 years. The STI incidencerate per 100,000 person-years rose from 35.3 beforeto 81.2 after PrEP start, with an aIRR of 1.35 (95% CI:1.18–1.56). Notably, this increase preceded PrEP initiation by 10–20 weeks. Specific aIRR for chlamydia, gonorrhoea and syphilis were 1.23 (95% CI: 1.03–1.48),1.24 (95% CI: 1.04–1.47) and 1.15 (95% CI: 0.76–1.72),respectively. In subanalyses for anatomical sites aIRRwas 1.26 (95% CI: 1.01–1.56) for rectal chlamydia and0.66 (95% CI: 0.45–0.96) for genital gonorrhoea.Conclusion: We found a 35% increase in STI incidenceassociated with PrEP use. It started before PrEP initiation, challenging the assumption that PrEP leadsto risk compensation. Instead, the data suggest thatindividuals seek PrEP during periods of heightenedsexual risk-taking. Consequently, PrEP programmesshould include sexual health consultations, STI testing, treatment and prevention strategies to preventHIV and improve sexual health.
Background: Pre-exposure prophylaxis (PrEP) effectively prevents HIV, but its association with sexually transmitted infections (STIs) has raised concerns about risk compensation, potentially impacting the expansion of PrEP programmes. Aim: We examined the relationship between PrEP and the incidence of chlamydia, gonorrhoea and syphilis. Methods: In this prospective cohort study, we compared STI rates before and after PrEP initiation among users in the capital region of Denmark (2019–2022), calculating incidence rate ratios adjusted for age and testing frequency (aIRR). To pinpoint when increases began, we plotted weekly STI rates, adjusting the timeline to correspond with PrEP initiation. Results: The study included 1,326 PrEP users with a median age of 35 years. The STI incidence rate per 100,000 person-years rose from 35.3 before to 81.2 after PrEP start, with an aIRR of 1.35 (95% CI: 1.18–1.56). Notably, this increase preceded PrEP initiation by 10–20 weeks. Specific aIRR for chlamydia, gonorrhoea and syphilis were 1.23 (95% CI: 1.03–1.48), 1.24 (95% CI: 1.04–1.47) and 1.15 (95% CI: 0.76–1.72), respectively. In subanalyses for anatomical sites aIRR was 1.26 (95% CI: 1.01–1.56) for rectal chlamydia and 0.66 (95% CI: 0.45–0.96) for genital gonorrhoea. Conclusion: We found a 35% increase in STI incidence associated with PrEP use. It started before PrEP initiation, challenging the assumption that PrEP leads to risk compensation. Instead, the data suggest that individuals seek PrEP during periods of heightened sexual risk-taking. Consequently, PrEP programmes should include sexual health consultations, STI testing, treatment and prevention strategies to prevent HIV and improve sexual health.