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Background: Changes in condom use and serosorting associated with HIV PrEP and treatment as prevention may be driving syphilis transmission in gay and bisexual men (GBM). We describe trends in syphilis testing and incidence among a large, national, retrospective cohort of GBM in Australia over a decade spanning PrEP implementation. Methods: Data were extracted from 55 sentinel clinics participating in the ACCESS project. GBM with ≥2 visits and ≥2 syphilis tests from Jan2012-Dec2021 were included in testing and incidence analyses, respectively. Annual rates of syphilis testing and diagnosis (primary, secondary, early-latent) per 100 person-years (py) were calculated disaggregated by HIV status and PrEP use (evidence of PrEP prescription; dichotomised as ever-PrEP vs never- PrEP). Poisson regression tested for trends from 2012-2021. Among those diagnosed with syphilis, rate of syphilis reinfection was calculated. Multivariable Cox regression explored risk factors for syphilis between 2016 (post-PrEP availability) to 2019 (pre-COVID). Results: 135,443 GBM (mean age=35.9 years; 7.8% with HIV; 31.0% ever-PrEP-users) had ≥2 visits and 93,918 GBM had ≥2 syphilis tests. There were 653,438 syphilis tests (median days between tests=119) over 610,996 person-years (testing rate=107.0/100py); testing was highest among GBM with HIV (152.2/100py). Between 2012-2021, testing increased from 68.3/100py to 132.7/100py (p< 0.001), mostly driven by increases among ever-PrEPusers [Figure]. There were 13,662 syphilis infections diagnosed in 9,546 (10.2%) GBM over 399,399 person-years (incidence rate=3.4/100py). Syphilis incidence was highest among GBM with HIV (6.7/100py), followed by ever-PrEP-users (3.7/100py) and never-PrEP-users (1.6/100py). Between 2012-2021, syphilis incidence increased among ever-PrEP-users from 1.4/100py to 5.0/100py (p< 0.001) and fluctuated between 5.8/100py and 7.4/100py among GBM with HIV. Rate of syphilis reinfection was 12.5/100py, and similar across groups. Ever previously diagnosed with syphilis (adjusted Hazard Ratio [HR]=2.63, 95%CI=2.45-2.82) was the strongest predictor of syphilis incidence, followed by recent (< 12m) syphilis diagnosis (aHR=2.04, 95%CI=1.89-2.20), living with HIV (aHR=2.07, 95%CI=1.94-2.23) and recently (< 12m) prescribed PrEP (aHR=1.91, 95%CI=1.77-2.06). Conclusions: Syphilis trends between GBM with HIV and GBM with evidence of PrEP use have been converging over the past decade. Previous syphilis infection was the strongest predictor of subsequent infection, highlighting the importance of including prior diagnosis as an indication for new targeted strategies (e.g., doxy-PEP). [ABSTRACT FROM AUTHOR]

Background: Doxycycline used as post-exposure prophylaxis (doxyPEP) within 72 hours of sex reduces the risk of bacterial sexually transmitted infections (STIs) in people assigned male sex at birth. Little is known about current use of antibiotics as STI prophylaxis in U.S. populations likely to benefit from doxyPEP., Methods: We conducted an online survey in September 2023 of U.S. adults recruited via sexual networking apps used mainly by gay and bisexual men (GBM). Respondents were asked about the use of antibiotics around the time of sex to prevent bacterial STIs., Results: Of 903 respondents, most (96.2%) identified as GBM; 19.0% were living with HIV and 42.5% using HIV pre-exposure prophylaxis. Half (49.1%) had heard of using antibiotics to prevent STIs and 95.6% were interested in use. Overall, 21.0% had used antibiotic STI prophylaxis and 15.9% had done so in the past year. Among those reporting any use, most (78.1%) had used doxycycline; some used amoxicillin (16.7%), azithromycin (14.5%), or other antibiotics (14.1%). Among those reporting use in the past year, 46.9% used it for some, 28.1% for most, and 25.0% for all sex acts with casual partners during that period. Most (78.3%) of STI prophylaxis users reported their condom use did not change during periods of STI prophylaxis use, 17.2% indicated their condom use declined, and 4.5% indicated their condom use increased. For doxyPEP specifically, 35.7% had heard of it and 13.0% had used it in the past year, of whom 21.0% had used a dosage other than the 200 mg dose shown to be effective., Conclusions: In this sample of primarily GBM, interest in bacterial STI prophylaxis was nearly universal. However, some of the use was not informed by current clinical guidance or evidence from research studies. Efforts are needed to increase awareness of effective dosing and monitor real-world use., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Sexually Transmitted Diseases Association.)