Hospitalizations of Children and Adolescents with Laboratory-Confirmed COVID-19 — COVID-NET, 14 States, July 2021–January 2022

Coinciding with increased circulation of the Omicron variant, COVID-19–associated hospitalization rates among children and adolescents aged 0–17 years increased rapidly in late December 2021, especially among children aged 0–4 years who are not yet eligible for vaccination. Throughout the periods of Delta and Omicron predominance, hospitalization rates remained lower among fully vaccinated adolescents aged 12–17 years than among unvaccinated adolescents.

The Omicron variant, which is associated with increased transmissibility and partial escape from infection- or vaccine-induced immunity, replaced Delta as the predominant variant in the United States in late December 2021 (1). Once the Omicron variant became predominant, peak population-based COVID-19–associated hospitalization rates among children and adolescents were four times as high as rates during the peak of the Delta period. Children aged 0–4 years, who were ineligible for vaccination during this time, experienced the largest increase in hospitalization rates. Observed indicators of severe COVID-19 among children and adolescents, in addition to the potential for longer-term sequelae (4,5), highlight the importance of multicomponent strategies to reduce the incidence of COVID-19, including vaccination of eligible persons and other prevention measures.

Among adolescents aged 12–17 years, the only pediatric age group for whom a COVID-19 vaccine was approved throughout the study period, December hospitalization rates among unvaccinated adolescents were approximately six times those among fully vaccinated adolescents, suggesting that vaccines were highly effective in preventing serious COVID-19 illness. Vaccination eligibility was expanded to include children aged 5–11 years on November 2, 2021. As of December 31, 2021, 54% of the population aged 12–17 years and 16% of those aged 5–11 years had completed a COVID-19 primary vaccination series. Increasing vaccination coverage among both age groups can reduce COVID-19–associated hospitalizations (6); enhanced outreach strategies are needed to address disparities in vaccination coverage by race/ethnicity.

Consistent with national hospital surveillance data (7), the findings in this report indicate that the Omicron-predominant period had higher rates of pediatric COVID-19 hospitalizations than the Delta-predominant period. No differences were found between the Delta- and Omicron-predominant periods in the proportion of hospitalizations that were likely to be related to COVID-19. Findings suggest that incidental admissions do not account for the increase in hospitalization rates observed during the Omicron period. Throughout the COVID-19 pandemic, admissions for reasons other than COVID-19 have been recorded (8,9), and during both the Delta- and Omicron-predominant periods, incidental admissions were more likely among fully vaccinated adolescents. Reasons for admission should continue to be monitored as more children and adolescents become fully vaccinated.

The findings in this report are subject to at least six limitations. First, COVID-19–associated hospitalizations might have been missed because of testing practices and test availability. Second, the period of Omicron variant predominance with available detailed clinical data is brief (December 19–31, 2021) and does not capture the peak of hospitalizations during the Omicron period; in addition, the Delta variant was still circulating in late December. Third, accounting for seasonality in comparisons of Delta and Omicron predominant periods was not possible. Fourth, the number of hospitalized children eligible for vaccination remained low at the time of reporting, and hospitalization rates stratified by vaccination status are subject to error if misclassification of vaccination status occurred. Fifth, because children aged 5–11 years could not meet the definition for being fully vaccinated until December 7, 2021, vaccination among this age group was not considered in this study. However, vaccinations could have affected hospitalization rates during the Omicron period. Further, boosters among adolescents aged 12–17 years could not be examined because the recommendation was so recent. Finally, the COVID-NET catchment areas include approximately 10% of the U.S. population; thus, these findings might not be generalizable to the entire United States.

Coinciding with the emerging predominance of the Omicron variant, rates of COVID-19–associated hospitalization among children and adolescents increased rapidly during the last 2 weeks of December 2021, especially among those aged 0–4 years. Moreover, among adolescents, hospitalization rates were higher among those who were unvaccinated. Vaccination of eligible persons, in addition to other prevention strategies such as masking, is critical to reducing the incidence of severe COVID-19 among children and adolescents. All persons who are eligible for vaccination should receive and stay up to date with COVID-19 vaccines to reduce the risk for severe disease for themselves and others with whom they come into contact, including children who are currently too young to be vaccinated

Citation: Marks KJ, Whitaker M, Anglin O, et al. Hospitalizations of Children and Adolescents with Laboratory-Confirmed COVID-19 — COVID-NET, 14 States, July 2021–January 2022. MMWR Morb Mortal Wkly Rep 2022;71:271–278. DOI: http://dx.doi.org/10.15585/mmwr.mm7107e4external icon.