P19. Surveillance of sexually transmitted infection (STI) incidence in a clinical cohort of men who have sex with men (MSM) on pre-exposure prophylaxis (prep): evidence from the sexual health clinic at Policlinico Umberto I in Rome

Abstract Background HIV prevention strategies have been revolutionized in the past few years. The introduction of pre-exposure prophylaxis (PrEP) has significantly enhanced prevention efforts, demonstrating high efficacy in reducing the HIV transmission risk. Accessing PrEP through sexual health clinics provides a strategic opportunity to address other health needs, particularly sexually transmitted infections (STIs). Recent studies have reported an increase in STI incidence, possibly due to evolving sexual behaviors and increased screening. With this study, we aimed to assess the incidence rate (IR) of STIs among a cohort of men who have sex with men (MSM) on PrEP at Policlinico Umberto I in Rome. Methods This observational study analyzed a total of 511 MSM on PrEP at Policlinico Umberto I in Rome, with an 18-month follow-up. For each individual we collected demographic data, such as age and race. The incidence of STIs was calculated as the number of new cases for each infection divided by the total time at risk. The 95% confidence intervals (CIs) were calculated using a Poisson distribution, and the results were reported per 100 person-years of follow-up (PYFU). Results Of the 511 participants, 393 (76.9%) were aged 27–49 years, and 408 (79.8%) were White. During the 18-month study period, incidence rates per 100 person-years of follow-up (PYFU) for STIs were 11.35 (95% CI: 9.00–13.83) for syphilis, 9.39 (95% CI:7.31–11.61) for urethritis, 2.74 (95% CI: 1.70–3.91) for proctitis, 1.17 (95% CI: 0.52–1.96) for HSV-2, 0.52 (95% CI: 0.13–1.04) for HCV, and 0.39 (95% CI: 0.00–0.91) for Monkeypox. No cases of HAV or HBV were reported. Additionally, two HIV seroconversions were observed over 766.5 PYFU [IR: 0.26/100 PYFU (95% CI: 0.00–0.65)]. All seroconversions occurred in individuals who reported poor adherence to PrEP. Conclusions The PrEP program is essential for HIV prevention and the monitoring of STIs. To better understand trends in STI incidence rates, we should investigate complementary prevention strategies, such as vaccination and post-exposure prophylaxis (PEP) for bacterial STIs. Regular screening remains crucial for the optimal management of sexual health in this population.