COVID-19-related hospitalization among infants and toddlers in the United States
COVID-19-related hospitalization among infants and toddlers in the United States

COVID-19-related hospitalization among infants and toddlers in the United States

In a recent study published in Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report (MMWR)Researchers studied coronavirus disease 2019 (COVID-19) -associated hospitalization among children and infants aged zero to four years in the United States (USA) during March 2020 and February 2022.

Examination: Hospitalization of infants and children aged 0-4 years with laboratory-confirmed COVID-19 – COVID-NET, 14 states, March 2020-February 2022. Image credit: Africa Studio / Shutterstock


The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron (B.1.1.529) variant became the predominant circulating strain in the United States after the end of December 2021. As B.1.1.529 circulation increased, COVID became -19-related hospitalization rates increased dramatically in neonates and children aged zero to four years, a population not yet eligible for SARS-CoV-2 vaccination.

In 99 counties spanning 14 states in the United States, the COVID-19-Associated Hospitalization Monitoring Network (COVID-NET) performs population-based monitoring of laboratory-certified SARS-CoV-2-related hospitalizations. Among the residents of a preset surveillance 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 hospitalization or during hospitalization.

About the study

This report evaluated the COVID-NET data to characterize the weekly SARS-CoV-2-associated hospitalization rates among U.S. children and infants aged zero to four years. The analysis has been completed from 1 Marchst, 2020 to 19 Februaryth, 2022, which covers the periods before Delta, under Delta and Omicron preponderance. The complete clinical information was available until 31 Januaryst, 2022

The total number of hospitalized patients was divided by the population estimates within each age category of the counties shown in the surveillance 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 ratio (RR) between Delta and Omicron dominant times and 95% confidence intervals (CIs) was determined. The three-week moving average was shown for the sake of visualization.

From March 2020 to November 2021, trained monitoring staff extracted medical records for all pediatric COVID-NET patients using a standardized case report. Information was collected on the main cause of hospitalization, viral co-detection, symptoms during hospitalization, underlying medical problems and markers of serious illness. Furthermore, the number of admissions to the intensive care unit (ICU) was determined monthly.


The results showed that during the Omicron overweight period in the United States, ie. on December 19thth2021 to 19 Februaryth2022, the weekly SARS-CoV-2-related hospitalization rates peaked per. 100,000 children and infants aged zero to four years in week 14.5 (week ending 8 Januaryth2022).

In addition, the peak of the Omicron-dominated period was about five times longer than the peak of the SARS-CoV-2 Delta (B.1.617.2) dominance period. Delta’s overweight period was from June 27thth2018, to 18 Decemberth2021, and its hospitalization rate peaked in the week ending September 11thth2021

Complete clinical information was available for 99%, 94% and 97% of the study population admitted before Delta, during Delta and during Omicron-dominated phases, respectively. During the Omicron-dominated period, 63% of hospitalized children and infants had no underlying medical problems.

In addition, infants younger than six months accounted for 44% of COVID-19-related admissions, despite no variation in severity markers by age. The proportion of infants under six months who were hospitalized during pre-Delta and Delta predominant periods also corresponded to the Omicron predominance by 46% and 43%, respectively.

The number of hospitalized COVID-19-positive children and infants co-detected with respiratory syncytial virus (RSV) infection was significantly higher in the Delta-dominant period than the Omicron-dominant period. The length of hospital stays and the need for ICU hospitalization were lower for the Omicron period than the Delta period. Nevertheless, monthly ICU admissions of the study population were almost 3.5 times greater at the peak of the Omicron overweight period than the Delta predominant peak. Hospital admissions among U.S. children and infants of zero to four years fell in the week ending Feb. 19th2022


The study results show that a significant percentage of children and infants aged between zero and four years were hospitalized with severe COVID-19 in all SARS-CoV-2 variants dominant periods in the United States. In addition, these age groups also have a high chance of long-term SARS-CoV-2 sequelae such as multisystem inflammatory syndrome. These data underline the importance of preventing COVID-19 among infants and children in this age category.

COVID-19 vaccination of currently qualified groups, such as family members, pregnant women and caregivers of newborns and young children, is an important strategy for the prevention of COVID-19 in infants and young children. While infants under six months of age are not currently eligible for COVID-19 vaccination, they obtain protection via passive transplacental transmission of SARS-CoV-2 vaccination-induced maternal antibodies. It should be noted that future studies are necessary to understand the potential long-term manifestations of SARS-CoV-2 in infants.

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