BACKGROUND: South Africa implemented universal test and treat (UTT) in September 2016 in an effort to encourage earlier initiation of antiretroviral therapy (ART). METHODS: We therefore conducted an interrupted time series (ITS) analysis to assess the impact of UTT on mean CD4 count at ART initiation among adults ≥16 years old attending 17 public sector primary care services in rural South Africa between July 2014 and March 2019. RESULTS: Among 20,599 individuals (69% women), CD4 counts were available for 74%. Mean CD4 at ART initiation increased from 317.1 cells/μL (95% confidence interval, CI, 308.6 to 325.6)-one to eight months prior to UTT-to 421.0 cells/μL (95% CI 413.0 to 429.0) one to twelve months after UTT, including an immediate increase of 124.2 cells/μL (95% CI 102.2 to 146.1). However, mean CD4 count subsequently fell to 389.5 cells/μL (95% CI 381.8 to 397.1) 13 to 30 months after UTT, but remained above pre-UTT levels. Men initiated ART at lower CD4 counts than women (-118.2 cells/μL, 95% CI -125.5 to -111.0) throughout the study. CONCLUSIONS: Although UTT led to an immediate increase in CD4 count at ART initiation in this rural community, the long-term effects were modest. More efforts are needed to increase initiation of ART early in HIV infection, particularly among men
