KP.2-Adapted BNT162b2 COVID-19 Vaccine Uptake and Effectiveness in Children.

Abstract

To assess the COVID-19 burden of disease, KP.2-adapted BNT162b2 COVID-19 vaccine uptake (2024-2025 formula), and vaccine effectiveness for children <5, 5-11, and 12-17 years of age. This retrospective cohort study used linked claims and vaccine registry data from California and Louisiana from August 22, 2024, to March 31, 2025. Inclusion criteria limited the sample to children without documented immunocompromised status and with complete demographic data. Vaccination status was treated as a time-varying exposure. The primary outcome was the composite of medically attended COVID-19 encounters in the emergency department, urgent care, or inpatient setting derived from administrative claims data. Analyses included incidence rates and, when possible, adjusted hazard ratios using Cox models. Among 2.6 million children aged <18 years who met the inclusion criteria, approximately 2% received a single dose of the KP.2-adapted BNT162b2 COVID-19 vaccine. The median follow-up was 7.4 months. Vaccinated children were more likely to reside in California, have commercial insurance, and have prior COVID-19 or influenza vaccination. Across age groups, the prevalence of underlying medical conditions was higher in children with medically attended COVID-19 (emergency department, urgent care, or inpatient setting). Vaccination was associated with significantly lower rates of medically attended COVID-19 across all age strata, with an associated 43% vaccine effectiveness pooled across all children aged <18 years (95% CI, 10-64). The KP.2-adapted BNT162b2 COVID-19 vaccine provided significant protection against emergency department, urgent care, and inpatient encounters for COVID-19 in children.