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.