In high-risk men who have sex with men (MSM) taking HIV pre-exposure prophylaxis (PrEP), the rates of sexually transmitted infections (STIs) were high but stable, according to a study published in JAMA Network Open. According to investigators, the findings suggest that some studies may overestimate the association between PrEP and STI incidence.

Investigators conducted a before-after analysis using a subcohort of a single-group PrEP implementation study, the Expanded PrEP Implementation in Communities in New South Wales (EPIC-NSW). STI testing data were extracted from a network of 54 sexual health clinics and 6 primary healthcare clinics from up to 1 year before enrollment and 2 years after enrollment. From the cohort of EPIC-NSW HIV-negative men with high-risk sexual behavior, MSM who were dispensed PrEP for the first time during the study, had 2 or more STI tests in the prior year, and a test during follow-up were included.

PrEP consisted of tenofovir disoproxil fumarate (300 mg) and emtricitabine (200 mg).


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A total of 2404 men with a mean age of 36 (SD, 10.4 years) were included in the before-after cohort. In the year prior to PrEP, mean STI testing frequency was 3.22 (SD, 1.44) per year and increased to 3.57 (SD, 1.79) tests per year in the 2 years after enrollment (difference, 0.35 test per year; 95%CI, 0.26-0.44 test per year; P <.001). The frequency of testing the first year after PrEP use was also higher with a mean of 4.45 (SD, 1.85) tests per year (difference, 1.23; 95% CI, 1.14-1.32; P <.001).

The proportion of positive STI tests in the year prior to PrEP was 50% (20.0% per quarter; 95% CI, 19.04%-20.95%) and was 52% (23.3% per quarter; 95% CI, 22.5%-24.2%) in the year after (difference, 1.4%; 95% CI, -1% to 4%; P =.34).

During 2 years of follow-up, 63% had a positive STI test. Before PrEP, 16% of participants had 2 or more positive results compared with 20% over a comparable duration of 1 year post-PrEP. When stratified by specific STI and anatomic site, the results were similar.

Limitations included infectious syphilis results being available for only a subset of publicly funded clinics. Also, the findings may not be generalizable to populations outside of this high-risk group, and it is possible that tests occurring at clinics besides the included health network were missed.

Investigators concluded that while STI incidence rates were already high and increased after PrEP was initiated, there was no increase in test positivity post-PrEP. This demonstrates the importance of considering preexisting STI and testing trends when investigating PrEP use and STI incidence, said investigators.

They also noted that the high STI positivity among men taking PrEP highlights the importance of STI control efforts among MSM.

Disclosure: Some study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

McManus H, Grulich AE, Amin J, et al. Comparison of trends in rates of sexually transmitted infections before vs after initiation of HIV preexposure prophylaxis among men who have sex with men. JAMA Netw Open. 2020;3(12):e2030806. doi:10.1001/jamanetworkopen.2020.30806