BNT162b2 XBB.1.5-Adapted Single Dose Vaccine Uptake and Effectiveness in Children Aged 5-17 Years Using Linked Claims and Vaccine Registries in California and Louisiana.

Abstract

To assess BNT162b2 XBB.1.5-adapted COVID-19 vaccine uptake and effectiveness in children aged 5-17 years against emergency department (ED) encounters, urgent care (UC) visits, and hospital admissions. We conducted a retrospective cohort study using HealthVerity claims tokenized to California and Louisiana state vaccine registries. Children were followed using a time-varying exposure definition, with vaccinated time ≥14 days after vaccination, from September 25, 2023 through March 31, 2024. Incidence and incidence rates were calculated for vaccinated and unvaccinated time. Time-dependent Cox models were used to estimate adjusted hazard ratios, with percent vaccine effectiveness calculated as (1 - hazard ratio)∗100. Of 2 449 261 children aged 5-17 years who met inclusion criteria, 34 389 (1.4%) received an XBB.1.5-adapted BNT162b2 vaccine. Vaccination uptake was higher in California than Louisiana and increased with age. Half (51.2%) of children who received the XBB.1.5-adapted vaccine had received a 2022-2023 season BA.4/5 bivalent COVID-19 vaccine. In contrast, the majority (66.0%) of XBB.1.5 unvaccinated children had not received any prior COVID-19 vaccine. For all measured outcomes, the XBB vaccinated children had significantly lower incidence rates compared with those who did not receive any XBB vaccine. There were no COVID-19 associated hospitalizations in the vaccinated group. Adjusted vaccine effectiveness among children aged 5-17 years was 63% (95% CI: 39%-77%) against COVID-19-associated ED/UC encounters with similar results stratified by age and among varying outcomes. BNT162b2 XBB.1.5-adapted formulations provided significant protection in children aged 5-17 years against COVID-19 associated hospitalization and ED or UC visits. NCT06199934 (https://clinicaltrials.gov/study/NCT06199934).