1. It is uncertain whether male circumcision (MC) reduces the risk of syphilis among men and women Partners PrEP Study data (n=4,716) analyzed to assess association of MC with incident syphilis in men and women RPR titer change of >4-fold with a Treponema pallidum–specific confirmatory result defined incident case MC status determined by physical examination and analyzed as time-varying 221 incident syphilis infections observed (99 in women, 122 in men) Background & Methods Male circumcision and the incidence of syphilis acquisition among male and female partners of HIV-1 serodiscordant heterosexual African couples: a prospective study Jillian Pintye 1, Jared Baeten 1, Lisa Manhart 1, Connie Celum 1, Allan Ronald 2,3, Nelly Mugo 1,4, Andrew Mujugira 1, Craig Cohen 4,5, Edwin Were 6, Elizabeth Bukusi 4,5, James Kiarie 1,7, Renee Heffron 1 For the Partners PrEP Study Team 1 University of Washington, 2 University of Manitoba, 3 Makerere University, 4 Kenya Medical Research Institute, 5 University of California-San Francisco, 6 Moi University, 7 University of Nairobi No conflicts of interest to disclose

2. Incident Syphilis & Risk Reduction Adj Hazard Ratio 1 p-value 0.58 (0.37-0.91) 0.017 0.38 (0.18-0.81) 0.013 0.64 (0.36-1.11) 0.115 0.41 (0.25-0.69) 0.001 0.52 (0.27-0.97) 0.040 0.25 (0.08-0.76) 0.014 Incidence rate (per 100 person-years) 1 Adjusted for age, sexual behavior, and plasma HIV-1 RNA levels of HIV-1 infected partner

3. LimitationsImplications Acknowledgements We are grateful to the couples who participated in this study University of Washington Coordinating Center and Central Labs: Connie Celum, Jared M. Baeten, Deborah Donnell, Robert W. Coombs, Lisa Frenkel, Craig W. Hendrix, Jairam Lingappa, M. Juliana McElrath. Site teams and partners: Kenneth Fife, Edwin Were (Eldoret, Kenya); Elioda Tumwesigye (Kabwohe, Uganda); Patrick Ndase, Elly Katabira (Jinja, Uganda); Elly Katabira, Allan Ronald (Kampala, Uganda); Elizabeth Bukusi, Craig Cohen (Kisumu, Kenya); Jonathan Wangisi, James Campbell, Jordan Tappero (Mbale, Uganda); James Kiarie, Carey Farquhar, Grace John-Stewart (Nairobi, Kenya); Nelly Rwamba Mugo (Thika, Kenya); James Campbell, Jordan Tappero, Jonathan Wangisi (Tororo, Uganda); DF/Net Research, Inc. (Data management); Contract Laboratory Services (Laboratory management); Gilead Sciences (Study drug donation) Funding was provided by the Bill and Melinda Gates Foundation (research grant OPP47674) and the National Institute of Child Health and Development (grants K99HD076679). Travel funds provided by the International AIDS Society Annual assessment of syphilis and MC status Absence of laboratory testing to link syphilis infections MC associated with decreased risk of syphilis in men and women MC may have benefits for syphilis prevention that expand its impact