Characteristics of HIV pre-exposure prophylaxis users at first PrEP counselling visit: the CSL-PrEP cohort.

Objectives: Pre-exposure prophylaxis (PrEP) is effective for HIV prevention and is mostly used by men who have sex with men (MSM). The aim of this study was to describe the characteristics of a cohort of PrEP users at first PrEP counselling visits (baseline, BL).

Design: Cross-sectional study of a cohort of MSM receiving PrEP (Centro San Luigi, CSL-PrEP Cohort).

Setting: Secondary-level sexually transmitted infections (STI) centre in Milan, Italy, from May 2017 to May 2022.

Participants: Overall, 624 MSM PrEP users were included; most users were Caucasian (97%), attended university (64%), with a median BL age of 34.5 years.

Results: Overall, 45% choose the daily-based PrEP regimen, 55% the event-based one. An increasing trend in PrEP counselling visits was observed (p=0.024). The majority had between 10 and 19 partners in the 3 months before BL and 41% were chemsex users. All had a HIV Incidence Risk Index for MSM (HIRI-MSM)>10, 54% between 20 and 29. Overall, 50% had ≥1 previous STI and 22% ≥1 BL STI. BL chlamydia (10%) was often more frequent than in the past (7%). The number of sexual partners was associated with BL chlamydia (p<0.001), gonorrhoea (p=0.002) and syphilis (p=<0.001), HIRI-MSM with chlamydia (p=0.001) and gonorrhoea (p=0.008), chemsex use with chlamydia (p=0.003) and gonorrhoea (p=0.030).

Conclusions: We observed an unbalanced access to PrEP in respect to all key populations which might benefit from PrEP, with a similar choice for event-based or daily-based regimens. High-risk behaviours and STIs were frequently observed. History of chlamydia was very frequently high in asymptomatic MSM at BL, compared with what observed before access to PrEP. High-risk behaviours and HIRI-MSM were associated with most of STIs.