The association between HIV treatment interruptions and viral suppression during the early treatment period: retrospective cohort study in South Africa

Background: The first six months after antiretroviral therapy (ART) initiation for HIV is a high-risk period for treatment interruptions that may compromise viral suppression (VS). Recent research in South Africa suggests that more than 40% of patients interrupt care for greater than 28 days during the early treatment period. The quantitative association between early treatment interruptions and VS at 6 and 12 months remains unclear. Methods: We enrolled adults (greater than or equal to18 years) initiating ART from 1 January 2018 to 7 November 2024 with at least 14 months followup in South Africas national ART database (TIER.Net) from 24 public sector facilities in four provinces. Engagement in care during months 0-6 and 7-12 was classified as continuous (no interruptions more than 28 days), cyclical (at least one interruption greater than 28 days but returned to care within follow up period), or disengaged (more than 28 days late without return), based on completed and scheduled visit dates. Modified Poisson regression was used to estimate adjusted risk ratios (aRRs) for VS (less than 50 copies/mL), adjusting for age, sex, initiation year, regimen, engagement pattern, and baseline CD4 count. Findings: Among 57,553 participants (66% female; median age 33 years), 49% and 42% were continuously engaged at 6 and 12 months, respectively; 22% and 17% were cyclically engaged at the same time points. 54% of continuously engaged participants achieved 6-month VS compared with 34% of those with cyclical engagement (aRR 1.60 95% CI 1.55-1.64). At 12 months, 56% of continuously engaged individuals and 40% of those cyclically engaged were suppressed (aRR 1.38 95% CI 1.34-1.42). VS was also associated with dolutegravir-based regimens, later ART initiation year, baseline CD4 count greater than 200 cells/uL, female sex, and older age. Interpretation: Even relatively brief treatment interruptions during the first year of ART were associated with substantially lower viral suppression. Preventing early interruptions should remain a programmatic priority to improve treatment outcomes.