Abstract
BACKGROUND: Tuberculosis (TB) remains a major global health challenge, and while TB preventive treatment (TPT) helps control it, in 2023, only ~ 42% of eligible household contacts under age 5 began TPT, with a median completion rate of 87% (IQR 74–95%) across reporting countries globally. This study analysed the effectiveness and factors related to isoniazid-based TPT (considered a public health strategy) in children under 5 years of age exposed to confirmed pulmonary TB cases in Medellín, Bello, and Itagüí, Colombia, “TPT” cohort, that was compared to a historic cohort (“non-TPT”) that did not receive TPT. METHODS: This cohort study included a qualitative component that explored knowledge about TB and children’s health care process as perceived by parents/caregivers and health care workers using of ethnographic strategies. The effectiveness measure of TPT was the occurrence of active TB. RESULTS: In the “TPT” cohort, 329 children met the inclusion criteria. Among these children, 74% were evaluated, 66% began treatment, 45% received TPT for six months, and 23.1% for nine months. Adverse events affected 11.1% of the treated children, mostly mild gastrointestinal symptoms (45.8% of all adverse events). At recruitment, the prevalence of active TB was 3.8% (n = 11), with 7 cases among indigenous children. No incident active TB cases were detected during follow-up. The “non-TPT” cohort included 240 children. Over two years, the cumulative incidence of active TB was 3.3%, with symptomatic cases at recruitment being diagnosed during follow-up. The adjusted period prevalence ratio was 0.77 (95% CI 0.2–2.4). The qualitative findings revealed three categories: (1) daily life and social conditions, including forced migration, influence TPT effectiveness; (2) the Colombian health system does not guarantee real access to TB diagnosis and treatment; and (3) stigma and differing perceptions of TB among families affect treatment outcomes. CONCLUSIONS: Isoniazid TPT effectively prevents TB in children; however, treatment-only strategies fall short of ensuring full coverage for children with TB infection. Determinants, including indigenous ethnicity and migration status, influence TB progression from infection to disease. More comprehensive approaches to TB are essential to address health system and socioeconomic barriers that create inequities in children’s access to care. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12879-026-12726-8.