Repeated syphilis episodes in HIV-infected men who have sex with men: a multicentre prospective cohort study on risk factors and the potential role of syphilis immunity

Open Forum Infectious Diseases 2020: , ISBN 2328-8957 (Journal)

Roth Jan A, Franzeck Fabian C, Balakrishna Suraj, Lautenschlager Stephan, Thurnheer Maria Christine, Trellu Laurence Toutous, Cavassini Matthias, Vernazza Pietro, Bernasconi Enos, Braun Dominique, Kouyos Roger D, Battegay Manuel, the Swiss HIV Cohort Study

Syphilis is re-emerging globally in general and HIV-infected populations and repeated syphilis episodes may play a central role in syphilis transmission among core groups. Besides sexual behavioural factors, little is known about determinants of repeated syphilis episodes in HIV-infected individuals ─ including the potential impact of preceding syphilis episodes on subsequent syphilis risk.In the prospective Swiss HIV cohort study with routine syphilis testing since 2004, we analysed HIV-infected men who have sex with men (MSM). Our primary outcome was first and repeated syphilis episodes. We used univariable and multivariable Andersen-Gill models to evaluate risk factors for first and repeated, incident syphilis episodes.Within the 14-year observation period, we included 2,513 HIV-infected MSM with an initially negative syphilis test. In the univariable and multivariable analysis, the number of prior syphilis episodes (adjusted HR [aHR] per one-episode increase, 1.15; 95% confidence interval [CI], 1.01 to 1.31), having occasional sexual partners with or without condomless anal sex (aHR, 4.99; 95% CI, 4.08 to 6.11; and aHR, 2.54; 95% CI, 2.10 to 3.07), and being currently on antiretroviral therapy (aHR, 1.62; 95% CI, 1.21 to 2.16) were associated with incident syphilis.In HIV-infected MSM, we observed no indication of decreased syphilis risk with repeated syphilis episodes. The extent of sexual risk behaviour over time was the strongest risk factor for repeated syphilis episodes. The observed association of antiretroviral therapy with repeated syphilis episodes warrants further immunological and epidemiological investigation.

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