Risk Factors for Severe and Critical Coronavirus Disease 2019 in Children.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is generally mild in children; however, severe or critical cases may occur. In this nationwide study, we analyzed clinical manifestations in children diagnosed with severe acute respiratory syndrome coronavirus 2 to identify high-risk groups for severe or critical disease and compared the clinical features between the Delta- and Omicron-dominant periods. METHODS: Data were retrieved from the National Health Insurance Service (NHIS) database and merged with the Korea Disease Control and Prevention Agency-COVID-19-NHIS cohort, which includes information on COVID-19 cases and vaccination records. We included individuals <20 years old diagnosed with COVID-19 during both periods (Delta: July 25, 2021-January 15, 2022; Omicron: January 16, 2022-March 31, 2022). RESULTS: Proportion of severe or critical cases was higher during the Delta period than during the Omicron period. The Omicron period saw increased hospitalization for pneumonia and croup and increased likelihood of hospitalization for neurological manifestations. The risk of severe COVID-19 depended on age group (Delta: highest for 12-19 years; Omicron: 0-4 years). This risk was high in children with multiple complex chronic conditions during both periods and with obesity or asthma during the Delta but not during the Omicron period. Two-dose COVID-19 vaccination provided strong protection against severe disease in the Delta period (adjusted odds ratio: 0.20), with reduced effectiveness in the Omicron period (adjusted odds ratio: 0.91). However, it significantly reduced the risk of critical illness (adjusted odds ratio: 0.14). CONCLUSIONS: These findings can facilitate identification of children at high risk of severe or critical COVID-19, who may require intensive medical support, and development of vaccination policies.

Effects of urinary tract infection during the first years of life in subsequent growth: a nationwide comparative matched cohort study.

Background: Although various childhood illnesses are known to influence growth status, the impact of urinary tract infections (UTI) on subsequent childhood growth remains unclear. This study was conducted to examine the association between UTI during infancy and growth status at 30-36 months. Methods: Nationwide population-based matched cohort study was done using data from the Korean National Health Insurance System (NHIS) and the Korean National Health Screening Program for Infants and Children (NHSPIC) between January 2018 and December 2020. Height and weight standard deviation scores (SDSs) at the fourth Korean NHSPIC conducted at 30-36 months were compared between children who experienced UTI during infancy and age- and sex-matched controls. We used weighted multiple linear regression analysis with inverse probability of treatment weighting (IPTW) and identified differences between the two groups using ß coefficient with corresponding 95% confidence intervals (CIs). Results: We analyzed 84,519 children diagnosed with UTI during infancy and 84,519 age- and sex-matched controls. The height SDS between children who experienced UTI and the control group was not statistically different (ß coefficient for height SDS, -0.0034; 95% CI: -0.0121 to 0.0054). However, the body mass index (BMI) SDS was significantly higher in children who had experienced UTI (ß coefficient for BMI SDS, 00426; 95% CI: 0.0304 to 0.0547). Subgroup and sensitivity analysis showed consistent results. Conclusions: Our findings suggest that a history of UTI during infancy is associated with high BMI measured at 30-36 months.