Dan-Yu Lin et al.

On October 29, 2021, the Food and Drug Administration authorized the BNT162b2 vaccine (Pfizer–BioNTech) for emergency use in children 5 to 11 years of age, on the basis of an immunobridging study and a small efficacy study.1 Recent case–control studies have shown modest short-term effectiveness of the BNT162b2 vaccine in this age group during the early phase of the period when the B.1.1.529 (omicron) vari- ant of severe acute respiratory syndrome corona- virus 2 (SARS-CoV-2) was spreading (from mid- December 2021 to mid-February 2022).2-4 We conducted a large cohort study over a 6 month period when the omicron variant was dominant. Here, we report on the protection conferred by the BNT162b2 vaccine and by previous SARS- CoV-2 infection against infection and coronavirus disease 2019 (Covid-19)–related hospitalization and death in children 5 to 11 years of age.