Does being on HIV antiretroviral therapy increase the risk of syphilis? An analysis of a large national cohort of MSM living with HIV in England 2009-2016.

While we observed a small increase in the rate of syphilis among those on ART, when adjusting for potential confounding factors, including a proxy measure for high-risk behaviour, there was no evidence of an increased risk of syphilis in MSM receiving ART. High-risk sexual behaviour markers were the main risk factors for syphilis, and our results highlight the need for STI prevention interventions in MSM living with HIV to target these particularly high-risk sexual networks.