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STI Risk Falls 80% After Milan MSM Get DoxyPEP Prescription
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HIVR4P 2024, Fifth HIV Research and Prevention Conference, October 6-10, 2024, Lima
Mark Mascolini
Only one quarter of men who have sex with men (MSM) with HIV or using PrEP to prevent HIV agreed to try doxycycline postexposure prophylaxis (DoxyPEP) to prevent bacterial sexually transmitted infection (STI) in Milan, Italy [1]. But in this 754-man retrospective real-life study, participants who used DoxyPEP had an 80% lower risk of bacterial STIs in the 11 months after a DoxyPEP prescription than in the 16 months before getting the chance to try this preventive strategy.
The study involved men seen at the Infectious Diseases Unit of San Raffaele Hospital in Milan. With 1.37 million people, Milan is the second most populous city in Italy and the commercial, fashion, and design center of the country.
Two randomized trials enrolling MSM living with HIV or taking PrEP to avoid HIV infection established that those who used DoxyPEP after risky sex with other men had significantly lower rates of new STIs [2,3]. A San Francisco/Seattle study of 501 MSM and transgender women found about 20% fewer visits with 1 or more STIs in people using DoxyPEP [2], while analysis of 232 MSM in France figured that those randomized to DoxyPEP halved their chance of picking up their first STI [3].
Milan researchers analyzed STI data collected from 197 MSM with HIV and 531 PrEP adopters without HIV [1]. To gauge the impact of DoxyPEP in fending off STIs, they compared the new-STI rate in the time after clinicians first offered DoxyPEP (called the baseline visit) with the new STI rate in the time before DoxyPEP prescription. Everyone had a least 1 year of follow-up before the baseline visit and at least 1 year after that visit. All men had an STI history, and all reported condom-free sex with 1 or more sex partners. Using DoxyPEP during the study period meant taking 200 mg of the antibiotic within 72 hours of intense sexual exposure, defined as sex with more than 5 partners.
The study group averaged 38.3 year in age, and 197 (26.1%) had HIV infection. Almost everyone with HIV, 98%, had an HIV load below 50 copies. Among the 754 MSM studied, 222 (29.4%) started DoxyPEP, including 153 PrEP users (28.8% of 531) and 69 men with HIV (35.0% of 197). The difference in DoxyPEP adoption between men with HIV and PrEP users did not reach statistical significance. Median follow-up time measured 15.8 months before DoxyPEP prescription and 10.8 months after DoxyPEP prescription.
Compared with men who did not use DoxyPEP, those who did had an HIV diagnosis for fewer years (10.5 vs 12.2, P = 0.046), had fewer years of potent antiretroviral therapy (9.11 vs 10.8, P = 0.030), had a higher nadir CD4 count (547 vs 410, P = 0.005,) and were more likely to have HCV antibody (9.4% vs 3.3%, P = 0.002) and more likely to have received 4CMenB vaccination against type B meningococcal disease (31.5% vs 18.6%, P < 0.001). Living with HIV versus using PrEP, age, and having hepatitis B surface antigen, a clinical AIDS diagnosis, an undetectable HIV load, and CD4 count did not differ significantly between men who used DoxyPEP and those who did not.
Before DoxyPEP prescription, the researchers counted 401 bacterial STIs, including 70 cases of syphilis, 139 cases of chlamydia, and 192 cases of gonorrhea. After DoxyPEP could be prescribed, participants had 146 STIs, including 26 cases of syphilis, 32 cases of chlamydia, and 88 cases of gonorrhea. Regression analysis determined that men who used DoxyPEP, had an 80% lower STI risk after versus before DoxyPEP prescription (incidence rate ratio 0.20, 95% confidence interval 0.17 to 0.25, P < 0.001. DoxyPEP users had an overall 7.0 days of therapy per 1000 person-days (median 5.35 days of therapy per 1000 person-days).
When people were counseled about DoxyPEP (before they could start using it), 25.7% of eventual DoxyPEP users versus 18.8% of nonusers had at least 1 concomitant STI (P = 0.043). Gonorrhea largely explained this difference (11.3% in DoxyPEP users vs 8.27% in nonusers, P < 0.001). Having at least 1 previous STI also proved significantly more likely in DoxyPEP users than in nonusers (74.3% vs 47.4%, P < 0.001), and that difference remained significant for chlamydia (37.8% vs 24.8%, P < 0.001), gonorrhea (48.6% vs 29.9%, P < 0.001), syphilis (18.0% vs 12.2%, P < 0.001), and mpox (18.0% vs 6.0%, P < 0.001). In this population of sexually active MSM with HIV or taking PrEP, rates of chlamydia, syphilis, and gonorrhea were all rising in the 2 years before DoxyPEP became available.
The Milan team concluded that MSM in this community started DoxyPEP at a "relatively moderate" rate when their clinicians first offered doxycycline as postexposure prophylaxis. But men with higher STI risk-reflected in higher prior STI rates-turned to PEP at a faster pace. Stably lower STI rates after DoxyPEP prescription began showed that "proper counseling' can promote continuing effectiveness of this strategy in MSM.
References
1. Raccagni AR, Diotallevi S, Lolatto R, et al. Doxycycline postexposure prophylaxis (DoxyPEP) real-life effectiveness in a cohort of men who have sex with men in Milan, Italy. HIVR4P 2024, Fifth HIV Research and Prevention Conference, October 6-10, 2024. Lima. Abstract PRC027.
2. Luetkemeyer AF, Donnell D, Dombrowski JC, et al. Postexposure doxycycline to prevent bacterial sexually transmitted infections. N Engl J Med. 2023;388:1296-1306. doi: 10.1056/NEJMoa2211934. https://www.nejm.org/doi/10.1056/NEJMoa2211934
3. Molina JM, Charreau I, Chidiac C, et al. Post-exposure prophylaxis with doxycycline to prevent sexually transmitted infections in men who have sex with men: an open-label randomised substudy of the ANRS IPERGAY trial. Lancet Infect Dis. 2018;18:308-317. doi: 10.1016/S1473-3099(17)30725-9.
https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(17)30725-9/fulltext
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