OBJECTIVE

This study aimed to provide evidence on trends related to the effects of coronavirus disease 2019 (COVID-19) vaccines (BNT162b2 and mRNA-1273) among children and adolescents in California during December 2021 through April 2023.

METHODS

We used a surveillance cohort study design to compare case and hospitalization incidence rate ratios (IRR) between vaccinated and unvaccinated children and adolescents considering age, dose received, and time since vaccination. We evaluated the Omicron BA.1/2 predominant period and the time from which vaccines became available to 1–4-year-olds through when administration of original strain monovalent doses was discontinued.

RESULTS

Across all age groups and time periods, vaccinated children were less likely to be hospitalized than unvaccinated children. For all but the youngest age group, vaccinated children were also less likely to have a documented COVID-19 infection. IRR for cases who received any mRNA vaccine primary series compared to unvaccinated children ranged from 1.13 (95% CI: 0.82, 1.55) for 1–4-year-olds to 0.21 (95% CI: 0.19, 0.23) for 12–17-year-olds. Hospitalization IRR ranged from 0.33 (95% CI: 0.16, 0.65) for 1-4-year-olds to 0.17 (95% CI: 0.13, 0.21) for 12–17-year-olds.

CONCLUSIONS

California surveillance data indicates that receipt of an mRNA vaccine was associated with reduced rates of COVID-19 infection and hospitalization across all childhood age groups. Although reductions in protection against infection appeared to be attenuated among the youngest age group, protection against hospitalization remained high for this population. Administration of COVID-19 vaccine is a valuable tool for reducing COVID-19 associated morbidity in children and adolescents.

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Competing Interests

CONFLICT OF INTEREST DISCLOSURES: The authors have no conflicts of interest relevant to this article to disclose.

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