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Background Pre-exposure prophylaxis (PrEP) is a cornerstone of HIV prevention, but PrEP users remain at substantial risk for bacterial STIs and risk compensation has been suggested as a potential contributor to this burden. Previous data from Italian cohort reported incidence rates (IR) of around 24, 23 and 13 per 100 PYFU for gonorrhoea (NG), chlamydia (CT) and syphilis (TP), respectively, with frequent subsequent infections. We assessed IRs of first and subsequent STIs in the PrIDE cohort and identified predictors of recurrent infections, to flag individuals at persistently high STI risk despite counselling and inform targeted prevention strategies.Methods We included PrEP users enrolled in the PrIDE cohort up to December [VM1.1][VM1.2]2025. Demographic, behavioural and clinical data were collected. STI prevalence at enrolment was assessed using samples collected within 28 days. IR of TP, NG and CT and of subsequent STI events were calculated per 100 person-years of follow-up. Time to first STI and to first subsequent event (defined at least 60 days after a previous positive test) was estimated using Kaplan–Meier (KM) analysis, stratified by symptomatic vs asymptomatic presentation when available.Predictors of STI occurrence and recurrence were assessed by a penalised Cox model, including doxyPEP use as a covariate.Results A total of 5.759 participants were included in the analysis. Most were male (5.674, 98.5%) with a median age of 37 years (IQR 31-45), and 65% had a university degree.Baseline prevalence was 8.2% for CT, 9.4% for NG and 3.4% for TP.IR/100 PYFU were 20.0 (17.9, 22.2) for CT, 25.0 (22.7, 27.4) for NG and 7.8 (6.5, 9.2) for TP.When stratified by symptomatic events, IRs were higher for symptomatic individuals: 48.8 (32.9, 69.6) for CT, 60.2 (42.3, 82.9) for NG and 30.9 (18.1, 48.2) for TP.Overall, 693 first events and 138 second events were observed over a median follow-up of 191 days. KM analysis showed a progressive increase in the probability of a first STI, mostly within the first year of follow-up. Symptomatic individuals exhibited a steeper early increase in cumulative incidence compared with asymptomatic individuals (figure 1). The cumulative incidence of a second STI increased more gradually over time (figure 2).A higher number of sexual partners in the last 3 months and student status were the strongest predictors of incident STI (figure 3).Conclusions In the PrIDE cohort, bacterial STIs remain frequent among PrEP users, with a substantial burden of early and recurrent events, particularly within the first year of follow-up and among symptomatic presentations. A higher number of recent sexual partners and student status emerged as key predictors of incident STIs. These findings highlight the need for intensified, risk-tailored prevention strategies focused on individuals at persistently elevated risk.Abstract OC29 Figure 1–3