High Baseline Prevalence and Stable Incidence of Chlamydia and Gonorrhea During the First Year of HIV Pre-Exposure...

Concerns persist that HIV pre-exposure prophylaxis (PrEP) may be associated with increased sexually transmitted infections (STIs), but longitudinal data incorporating the pre-PrEP period and standardized screening remain limited.

We conducted a retrospective cohort study of individuals initiating oral emtricitabine/tenofovir disoproxil fumarate PrEP at 2 STI clinics in Milan, Italy (2018-2024). Participants underwent baseline and quarterly screening (pharyngeal, anal, vaginal swabs and urine nucleic acid amplification testing) for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG). We estimated baseline prevalence and interval-specific conditional cumulative incidence across 0 to 3, 3 to 6, 6 to 9, and 9 to 12 months intervals, and described symptomatic and recurrent diagnoses. Finally, we evaluated STI trends across 3 calendar periods: 2018 to 2019, 2020 to 2021, and 2022 to 2024.

A total of 1087 individuals were included (median age 35 years [interquartile ranges 30-41]); most were cisgender gay, bisexual, and other men who have sex with men (98.4%). At baseline, 15% (163/1,087) had at least one CT/NG infection. During follow-up, 516 new diagnoses occurred in 359 individuals (33%). Interval-specific conditional cumulative incidence for any CT/NG infection was 13.5%, 15.2%, 17.7%, and 12.7% across the 4 intervals. The majority of infections were asymptomatic. No substantial differences in STI trends were observed across the 3 calendar periods.

In this real-world PrEP cohort undergoing quarterly nucleic acid amplification testing screening, CT/NG diagnoses were common at baseline and maintained high but stable incidence during the first year after PrEP initiation, with no clear upward trend over time.