2024 Yes https://doi.org/10.5365/wpsar.2024.15.3.1077 Vu, Trang Thu Asia Observational Epidemiology Study Students Elementary (K-5) Middle/Jr High (6-8) High School (9-12) Viruses COVID rates This retrospective cohort study analyzed 157 students and 540 contacts during three COVID-19 outbreaks in Viet Nam. Household secondary attack rate was 24.6%, and vaccine effectiveness was 39%, supporting household vaccination during school outbreaks.