AIDS

Emerging evidence suggests that risk of bacterial sexually transmitted infections (STIs); increases among gay and bisexual men; following initiation of HIV preexposure prophylaxis (PrEP). To describe STI incidence and behavioral risk factors; among a cohort of predominantly gay and bisexual men; who use PrEP, and to explore changes in STI incidence; following PrEP commencement. The Pre-exposure Prophylaxis Expanded (PrEPX) Study, a multisite, open-label intervention study, nested within the Australian Collaboration for Coordinated Enhanced Sentinel Surveillance (ACCESS) clinic network.
A total of 4275 participants, enrolled in Victoria, Australia. Of these, 2981 enrolled at 5 ACCESS clinics (3 primary care, 1 sexual health, and 1 community-based HIV rapid testing service); had at least 1 follow-up visit, and monitored. Upon enrollment, participants received daily oral tenofovir disoproxil fumurate; and emtricitabine for HIV PrEP, quarterly HIV and STI testing; and clinical monitoring. The primary outcome was incidence of chlamydia, gonorrhea, or syphilis. Incidence rates and hazard ratios; describing behavioral risk factors of STI diagnosis calculated. Incidence rate ratios (IRRs), adjusted for change in testing frequency, described changes in STI incidence from 1-year preenrollment to study follow-up among participants with preenrollment testing data (n = 1378).

Group sex associated with greater STI risk

Among the 2981 individuals, 98.5% identified as gay or bisexual males, 29% used PrEP prior to enrollment, 89 (3%) withdrew and were censored at date of withdrawal, leaving 2892 enrolled at final follow-up. However, during a mean follow-up of 1.1 years (3185.0 person-years), 2928 STIs were; diagnosed among 1427 (48%) participants. So, STI incidence was 91.9 per 100 person-years, with 736 participants (25%) accounting for 2237 (76%) of all STIs. Among 2058 participants with complete data for multivariable analysis; younger age, greater partner number, and group sex were; associated with greater STI risk, but condom use was not.

So, among 1378 participants with preenrollment testing data, STI incidence increased from 69.5 per 100 person-years prior to enrollment to 98.4 per 100 person-years during follow-up. However, after adjusting for testing frequency, the increase in incidence from 1 year preenrollment to follow-up was significant for any STI (adjusted IRR, 1.12 [95% CI, 1.02-1.23]) and for chlamydia. For gay and bisexual men, receipt of HIV preexposure prophylaxis (PrEP) is associated with an increase in sexually transmitted infections (STIs), according to a study published in the Journal of the American Medical Association. Michael W. Traeger, from the Burnet Institute in Melbourne, Australia, and colleagues describe STI incidence and behavioral risk factors among a cohort of 2,981 predominantly gay and bisexual men (98.5 percent) who use PrEP.

Gay and bisexual men using PrEP, STIs

So, participants received daily oral tenofovir disoproxil fumarate and emtricitabine for HIV PrEP upon enrollment, quarterly HIV and STI testing, and clinical monitoring. The researchers found that 2,928 STIs were; diagnosed among 1,427 participants during a mean follow-up of 1.1 years. The incidence of STIs was 91.9 per 100 person-years, with 25% of participants accounting for 76% of all STIs. Younger age, greater partner number, and group sex were; associated with greater STI risk, but condom use was not; among 2,058 participants with complete data for multivariable analysis. From before enrollment to follow-up, the incidence of STIs increased from 69.5 to 98.4 per 100 person-years (incidence rate ratio [IRR], 1.41).

The increase in incidence from one year before enrollment to follow-up was significant for any STI and for chlamydia (adjusted IRRs, 1.12 and 1.17, respectively). “These findings highlight the importance of frequent STI testing among gay and bisexual men using PrEP,” the authors write. Several authors disclosed financial ties to the pharmaceutical industry. So, among gay and bisexual men using PrEP, STIs were highly; concentrated among a subset, and receipt of PrEP after study enrollment; associated with an increased incidence of STIs compared with preenrollment. Howevr, these findings highlight the importance of frequent STI testing among gay and bisexual men using PrEP.