In a recent study published in the Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report (MMWR), researchers investigated coronavirus disease 2019 (COVID-19)-associated hospitalization among children and infants aged zero to four years in the United States (US) during March 2020 and February 2022.
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron (B.1.1.529) variant became the predominant circulating strain in the US after late December 2021. As B.1.1.529 circulation increased, the COVID-19-related hospitalization rates rose dramatically in newborns and children aged zero to four years, a population not yet eligible for SARS-CoV-2 vaccination.
In 99 counties spanning over 14 states of the US, the COVID-19–Associated Hospitalization Monitoring Network (COVID-NET) performs population-based monitoring for laboratory-confirmed SARS-CoV-2–related hospital admissions. Among the inhabitants of a preset monitoring catchment area, SARS-CoV-2-related hospitalizations are described as receiving a positive COVID-19 rapid antigen detection or real-time reverse transcription-polymerase chain reaction (RT-rtPCR) test result 14 days before hospital admission or during hospitalization.
About the study
The present report evaluated the COVID-NET data to characterize the weekly SARS-CoV-2-associated hospitalization rates among US children and infants of zero to four years of age. The analysis was conducted from March 1st, 2020, to February 19th, 2022, covering the periods before Delta, during Delta, and Omicron predominance. The complete clinical information was available until January 31st, 2022.
The total number of patients hospitalized was divided by the population estimates inside every age category for the counties shown in the monitoring catchment area to generate unadjusted weekly SARS-CoV-2–related hospitalization rates. All rates were calculated per 100,000 newborns and children aged zero to four years. The rate ratios (RR) between Delta- and Omicron-predominant times and 95% confidence intervals (CIs) were determined. Three-week moving averages were shown for the sake of visualization.
From March 2020 to November 2021, trained surveillance personnel abstracted medical records for all pediatric COVID-NET patients utilizing a standardized case report sheet. Information about the main reason for hospitalization, viral co-detections, symptoms during admission, underlying medical problems, and markers of serious illness were collected. Further, intensive care unit (ICU) admissions rates were determined monthly.
The results indicated that during the Omicron predominance period in the US, i.e., December 19th, 2021, to February 19th, 2022, the weekly SARS-CoV-2–related hospitalization rates per 100,000 children and infants aged zero to four years peaked at week 14.5 (week ending of January 8th, 2022).
Moreover, the peak of the Omicron-predominant period was around five-fold longer than the peak of the SARS-CoV-2 Delta (B.1.617.2) predominance period. Delta’s predominance period was from June 27th, 2018, to December 18th, 2021, and its hospitalization rate peaked during the week ending September 11th, 2021.
Complete clinical information was available for 99%, 94%, and 97% of the study population hospitalized before Delta, during Delta, and during Omicron-predominant phases, respectively. During the Omicron-predominant period, 63% of hospitalized children and infants did not have any underlying medical issues.
In addition, infants younger than six months constituted 44% of COVID-19-related hospitalizations, despite no variations in severity markers by age. The proportion of infants less than six months of age hospitalized during pre-Delta and Delta predominant periods were also similar to the Omicron predominance at 46% and 43%, respectively.
The number of hospitalized COVID-19-positive children and infants co-detected with respiratory syncytial virus (RSV) infection was substantially high during the Delta-predominant period than the Omicron-predominant period. The length of hospital stay and need for ICU admission was lower for the Omicron period than the Delta period. Nevertheless, monthly ICU admissions of the study population were nearly 3.5-fold greater in the peak of the Omicron-predominance period than the Delta-predominant peak. Hospitalizations among US children and infants of zero to four years declined by the week ending February 19th, 2022.
The study findings show that a significant percentage of children and infants aged between zero to four years were hospitalized with severe COVID-19 during all SARS-CoV-2 variant predominant periods in the US. Furthermore, these age groups also have a high chance for long-term SARS-CoV-2 sequelae such as multisystem inflammatory syndrome. These data underscore the importance of preventing COVID-19 among infants and children of this age category.
COVID-19 vaccination of presently eligible groups, such as family members, pregnant women, and caregivers of newborns and young children, is a significant strategy for preventing COVID-19 in infants and young kids. While infants younger than six months are currently not eligible for COVID-19 vaccination, they acquire protection via passive transplacental transmission of SARS-CoV-2 vaccination-induced maternal antibodies. Of note, future investigations are required to understand the potential long-standing manifestations of SARS-CoV-2 in infants.