Abstract

Impact of Pre-Exposure Prophylaxis (PrEP) on Sexually Transmitted Infection (STI) incidence among Men who have Sex with Men (MSM) in Mecklenburg County North Carolina.

Objective: This study aims to determine whether MSM who were prescribed Truvada for Pre-Exposure Prophylaxis (PrEP) have a higher incidence of Sexually Transmitted Infections (STIs) than MSM not using Truvada for PrEP.

Design: Primary analysis of longitudinal STI data obtained from MSM attending Rosedale Medical and Amity Medical Group in Charlotte North Carolina, USA, and January 2016-October 2018.

Methods: Men who have Sex with Men (MSM) individuals were identified and grouped into two, those who were prescribed PrEP and a second group not using PrEP (propensity score was used to match similar individuals). Patients’ STI data was used to compare the incidence of chlamydia, gonorrhea, and syphilis, and time to first symptomatic STI among PrEP users and nonusers.

Results: Propensity score matched 98 PrEP users to nonusers included in the analysis. Incidence Rate Ratios (IRRs) for chlamydia, gonorrhea and early syphilis were 3.2 {95% confidence interval (95% CI): 1.9-5.3}, 2.8 (95% CI: 1.7-4.6) and 2.9 (95%CI: 1.5-5.6), respectively, comparing PrEP users to nonusers. Time to first symptomatic STI was shorter among PrEP users (120 days, 95% CI: 77- 171) than among nonusers (185 days, 95% CI: 163-256).

Conclusion: Among MSM on PrEP, we observed a higher incidence of STIs and faster time to first symptomatic STI than MSM, not on PrEP. PrEP nonusers had a higher incidence of syphilis compared to PrEP users. However, there is insufficient evidence that PrEP maybe a contributing factor in increasing STI rates among MSM.

Keywords: Human Immunodeficiency Virus (HIV); Propensity- score; Survival analysis; Truvada; Pre-Exposure Prophylaxis (PrEP); Sexually Transmitted Infections (STI); Men who have Sex with Men (MSM)