Incidence and Risk of Coronavirus Disease 2019 Hospitalization Among Unvaccinated Children

Objectives

The aim of this study is to determine the incidence and risk factors associated with COVID-19 hospitalization among unvaccinated children.

Methods

Children aged 0– < 18 years, members of Kaiser Permanente Northern California (KPNC), were followed from March 1, 2020, until the earliest occurrence of: chart-confirmed COVID-19 hospitalization, disenrollment from KPNC, age 18 years, receipt of COVID-19 vaccine, death, or study end (December 31, 2022). We calculated the incidence rate of hospitalization by SARS-CoV-2 variant period and by age group. We determined risk factors for hospitalization using Poisson regression. We also conducted descriptive analyses of hospitalized cases.

Results

Among 1,107,799 children, 423 were hospitalized for COVID-19 during follow-up. The incidence of hospitalization increased with each new SARS-CoV-2 variant and was highest among children aged < 6 months. Among the < 6-month-olds, the incidence rate per 100,000 person-months was 7 during predelta, 13.3 during delta, and 22.4 during omicron. Black (RR = 2.05, 95% CI: 1.33–3.16) and Hispanic children (RR = 1.82, 95% CI: 1.34–2.46) and children with any comorbidities were at high risk of hospitalization (RR = 3.81, 95% CI: 2.94–4.95). Overall, 20.3% of hospitalized children were admitted to an intensive care unit (ICU), but ICU admission was 36.1% among 12– < 18-year-olds. The majority of ICU admits (91.8%) had no comorbidities.

Conclusion

Children too young to be vaccinated had the highest incidence of COVID-19 hospitalization, while adolescents had the highest proportion of ICU admissions. To prevent severe disease in children and adolescents, everyone eligible should be vaccinated.