Study population and setting
This surveillance study used data from COVID-NET, a COVID-19-associated hospitalization surveillance network, to describe COVID-19-associated hospitalizations among US children and adolescents (0-17 years) to compare disease severity from before and after the Delta variant became the predominant strain in the US (March 1, 2020 to August 14, 2021). The COVID-NET catchment area consists of 99 counties across 14 states. Cases were defined as residents who were diagnosed with laboratory-confirmed SARS-CoV-2 in the 14 days before, or during, hospitalization. Study staff collected measures of disease severity (length of stay, highest level of breathing support, blood pressure support, and in-hospital death) and vaccination status of all hospitalized children. Age-specific (0-4 years, 5-11 years, and 12-17 years) cumulative and weekly COVID-19-associated hospitalizations per 100,000 children were calculated by dividing COVID-19-associated hospitalizations by 2019 age-specific population estimates for the included counties from the National Center for Health Statistics’ population estimates. The study used COVID-NET vaccination data on hospitalized adolescents (12-17 years) and state immunization databases to calculate cases per 100,000 person-weeks for vaccinated and unvaccinated adolescents. They compared age-specific hospitalizations and hospitalizations among fully vaccinated and unvaccinated adolescents from June 20, 2021 to July 31, 2021. Disease severity measures from March 1, 2020 to June 19, 2021 were compared with those from June 20, 2021 to July 31, 2021.
Summary of Main Findings
From March 1, 2020 to August 14, 2021, there were 49.7 cumulative COVID-19-associated hospitalizations per 100,000 children and adolescents, aged 0-17 years. The burden was similar among younger children (0-4 years, 69.2 hospitalizations) and adolescents (12-17 years, 63.7 hospitalizations), but lower among children aged 5-11 years (24.0). Weekly hospitalizations were lowest from June 12 to July 3, 2021 (0.3 per 100,000 in younger children and adolescents) after their peak of 1.5 in January 2021. With the predominance of the Delta variant in July and August 2021, weekly incidence increased to 4.7 times the lowest rate from June 2020 (0.3) in the week ending August 14, 2021 (1.4). Across all time periods, COVID-19-associated hospitalizations were more common in children aged 0-4 years and adolescents aged 12-17 years than among children aged 5-11 years. From June 20 to July 31, 2021, the hospitalization rate among unvaccinated adolescents (0.8 per 100,000; 95% CI 0.6, 0.9) was significantly higher than among fully vaccinated adolescents (0.1, 95% CI 0, 0.1) (RR=10.1; 95% CI 3.7, 27.9). Finally, although rates increased with the spread of the Delta variant, disease severity was not significantly different before or after June 19, 2021 – approximately 26% were admitted to the intensive care unit (ICU) during both time periods.
This study included a large number of child and adolescent COVID-19-associated hospitalizations across the United States over a period of time before and after the emergence of the Delta variant in the US.
Due to the short amount of time adolescents have been eligible for the COVID-19 vaccine and the relatively low relative COVID-19-associated hospitalizations (compared to adults), the estimates of the relative risk of hospitalizations in vaccinated versus unvaccinated adolescents is fairly imprecise and did not account for potential confounding variables (such as medical comorbidities). Furthermore, it is possible that cases classified as COVID-19-associated hospitalizations may have included cases where an individual was hospitalized and tested positive for SARS-CoV-2, but was not hospitalized for COVID-19. This would bias the rate estimates upwards. It is also unclear how the child and adolescent populations within the selected counties changed since 2019, which may bias the rate estimates upwards or downwards. Finally, this study cannot comment on the proportion of children and adolescents infected with SARS-CoV-2 who were sick enough to warrant hospitalization for COVID-19.
This study presents new data that COVID-19-associated hospitalizations increased with the emergence of the Delta variant and that 0-4 year olds and 12-17 year olds have been more likely to have COVID-19-associated hospitalizations than 5-11 year olds in the United States.
This review was posted on: 2 November 2021