Increased Incidence of STIs in Gay/Bisexual Men Who Received HIV PrEP

Increased Incidence of STIs in Gay/Bisexual Men Who Received HIV PrEP

May 7, 2019 Bradley van Paridon

An increased incidence of sexually transmitted infections (STIs) was associated with the receipt of HIV pre-exposure prophylaxis (PrEP) in gay and bisexual men, according to data published in JAMA.

To describe the STI incidence and behavioral risk factors in a cohort of gay and bisexual men using PrEP and the changes in STI incidence after PrEP initiation, a total of 2981 participants were enrolled who had at least 1 follow-up visit and were monitored from July 26, 2016, to April 30, 2018.

Of the 2981 individuals enrolled, 98.5% identified as gay or bisexual males and 29% used PrEP before enrollment. On enrollment, participants received daily oral tenofovir disoproxil fumarate and emtricitabine for HIV PrEP, quarterly HIV and STI testing, and clinical monitoring.

At the time of final follow-up 2892 participants remained enrolled, and during a mean follow-up of 1.1 years, 2928 STIs were diagnosed in 48% (n=1427) of participants. Etiologies of STIs included 1434 cases of chlamydia, 1242 of gonorrhea, and 252 of syphilis. The incidence of STIs was 91.9 per 100 person-years, with 25% or participants accounting for 76% of all STIs.

Complete data for multivariable analysis were available for 2058 participants, and those of younger age; with greater numbers of sexual partners; who had a diagnosis of rectal gonorrhea, chlamydia, or syphilis; and who engaged in group sex were significantly associated with greater risk for STI, but condom use was not. Pre-enrollment data were available for 1378 participants and showed that STI incidence increased from 69.5 per 100 person-years before enrollment to 98.4 per 100 person-years during follow-up (incidence rate ratios [IRRs], 1.41; 95% CI, 1.29-1.56). The increase in incidence from 1 year pre-enrollment to follow-up was significant after adjusting for testing frequency for any STI (adjusted IRR, 1.12; 95% CI, 1.02-1.23) and for chlamydia (adjusted IRR, 1.17; 95% CI, 1.04-1.33).

The study investigators noted several study limitations, including factors that reduced the generalizability of the data. Specifically, they noted that early adopters of PrEP are typically individuals whose attendant STI risk is high, and participants included in the before-and-after analysis were those accessing STI screening at ACCESS clinics before enrollment. A comparative analysis found that participants accessing screening at ACCESS were more likely to report methamphetamine use and to report having more than 1 episode of condomless insertive anal intercourse with a partner of unknown HIV status or a partner with HIV not taking antiretroviral treatment in the 3 months before enrollment. Researchers also acknowledged the possibility that those lost to follow-up may have differential STI risks compared with those not lost. Further, behavioral responses also relied on self-reporting.

Further limitations were that some participants may have some sought treatment for STIs at nonparticipating clinics, and data on STI treatments prescribed to participants were also not collected, meaning it could not be ensured that every STI was treated effectively and that all positive diagnoses were incident infections. In addition, the study investigators did not report on the incidence of STIs in patients who might have used the medication in an on-demand fashion; therefore, “[i]t will be important to evaluate the incidence of STIs among individuals using on-demand [PrEP] in future studies,” noted the study investigators.

The results demonstrated that STIs were concentrated in a subset of participants, and that receipt of PrEP after enrollment was associated with increased incidence of STIs. Researchers concluded that these findings “highlight the importance of frequent STI testing among gay and bisexual men using PrEP.”