Davies, Mary-AnnMary-AnnDaviesMoultrie, HarryHarryMoultrieEley, BrianBrianEleyRabie, HelenaHelenaRabieVan Cutsem, GillesGillesVan CutsemGiddy, JanetJanetGiddyWood, RobinRobinWoodTechnau, KarlKarlTechnauKeiser, OliviaOliviaKeiser0000-0001-8191-2789Egger, MatthiasMatthiasEgger0000-0001-7462-5132Boulle, AndrewAndrewBoulle2024-10-112024-10-112011https://boris-portal.unibe.ch/handle/20.500.12422/77773Background: With expanding pediatric antiretroviral therapy (ART) access, children will begin to experience treatment failure and require second-line therapy. We evaluated the probability and determinants of virologic failure and switching in children in South Africa. Methods: Pooled analysis of routine individual data from children who initiated ART in 7 South African treatment programs with 6-monthly viral load and CD4 monitoring produced Kaplan-Meier estimates of probability of virologic failure (2 consecutive unsuppressed viral loads with the second being >1000 copies/mL, after ≥24 weeks of therapy) and switch to second-line. Cox-proportional hazards models stratified by program were used to determine predictors of these outcomes. Results: The 3-year probability of virologic failure among 5485 children was 19.3% (95% confidence interval: 17.6 to 21.1). Use of nevirapine or ritonavir alone in the initial regimen (compared with efavirenz) and exposure to prevention of mother to child transmission regimens were independently associated with failure [adjusted hazard ratios (95% confidence interval): 1.77 (1.11 to 2.83), 2.39 (1.57 to 3.64) and 1.40 (1.02 to 1.92), respectively]. Among 252 children with ≥1 year follow-up after failure, 38% were switched to second-line. Median (interquartile range) months between failure and switch was 5.7 (2.9-11.0). Conclusions: Triple ART based on nevirapine or ritonavir as a single protease inhibitor seems to be associated with a higher risk of virologic failure. A low proportion of virologically failing children were switched.enarticle10.7892/boris.73182110726600028786430002410.1097/QAI.0b013e3182060610