Traeger MW, et al. - Researchers examined 2,981 mostly gay and bisexual men—who received daily HIV preexposure prophylaxis—for sexually transmitted infection (STI) incidence, behavioral risk factors, and modifying effects of preexposure prophylaxis (PrEP) commencement on STI incidence. According to findings, among gay and bisexual men using PrEP, STIs were highly concentrated among a subset, and receipt of PrEP following study enrollment was linked to a higher incidence of STIs vs pre-enrollment. These findings, thus, underscore the importance of regular STI testing among gay and bisexual men using PrEP.

Methods

• The Pre-exposure Prophylaxis Expanded (PrEPX) Study was nested within the Australian Collaboration for Coordinated Enhanced Sentinel Surveillance (ACCESS) clinic network.
• Among 4,275 participants enrolled (late July 2016 to April 1, 2018), a total of 2,981 had ≥ 1 follow-up visit at five ACCESS clinics and were monitored until April 30, 2018.
• Participants received daily oral tenofovir disoproxil fumurate and emtricitabine for HIV PrEP, quarterly HIV and STI testing, and clinical monitoring.
• The incidence of chlamydia, gonorrhea, or syphilis was assessed as the primary outcome.
• Calculation of incidence rates and hazard ratios describing behavioral risk factors of STI diagnosis was also done.
• Among participants with pre-enrollment testing data (n=1.378), changes in STI incidence from 1-year pre-enrollment to study follow-up was determined via incidence rate ratios (IRRs), adjusted for change in testing frequency.

Results

• In all, 98.5% of the 2,981 participants were homosexual or bisexual males.
• PrEP use was reported in 29% prior to enrollment, and 3% withdrew and were censored at date of withdrawal, leaving 97.0% enrolled at final follow-up.
• A total of 2,928 STIs were reported among 48% of participants during a mean follow-up of 1.1 years (1,434 chlamydia, 1,242 gonorrhea, and 252 syphilis).
• Researchers noted STI incidence of 91.9 per 100 person-years, with 736 participants accounting for 76% of all STIs.
• Multivariable analysis of 2,058 participants who had complete data available indicated greater STI risk in correlation with younger age, greater partner number, and group sex—but not with condom use.
• Increase in STI incidence from 69.5 per 100 person-years prior to enrollment to 98.4 per 100 person-years during follow-up was observed among 1,378 participants with pre-enrollment testing data.
• For any STI and for chlamydia, the increase in incidence from 1-year pre-enrollment to follow-up was significant after adjusting for testing frequency.