Efficacy of Isoniazid-Rifampicin Preventive Therapy in Adolescent Contacts in School Outbreaks: A Retrospective Cohort Study in Eastern China.

Adolescents are underprioritized in tuberculosis (TB) control, and the effect of TB preventive therapy (TPT) in this group is unstudied in China. This study evaluated the protective effect of TPT in Chinese adolescents during TB outbreaks. Data on TB outbreaks and contact screening in six cities (2019-2021) were collected. Adolescents eligible for TPT were identified via tuberculin skin test or interferon-gamma assay and grouped by TPT. Follow-up until 31 December 2023, tracked TB onset. The protective effect was analyzed using KM survival curves and COX models. From January 2019 to December 2021, 136 school TB outbreaks were reported, involving 10,837 adolescent contacts. Among these, 624 adolescent contacts met the criteria for TPT (latent TB infection) at baseline; 277 (44.4%) initiated a 3-month isoniazid plus rifampicin preventive therapy (TPT group), while 347 (55.6%) did not receive TPT (non-TPT group). By 31 December 2023, 11 of these 624 adolescent contacts developed active TB, with 1 patient in the TPT group and 10 patients in the non-TPT group. The cumulative incidence of TB was 0.36% in the TPT group vs. 2.88% in the non-TPT group (χ2 = 5.65, p = 0.017). This corresponds to an approximate 87% reduction in TB incidence among adolescent contacts who received TPT compared to those who did not. TPT reduced TB incidence by ~90% among adolescent contacts. Timely, comprehensive, and standardized TPT is recommended to minimize TB risks in educational settings and achieve a TB-free campus.