J Korean Med Sci.  2023 Mar;38(9):e65. 10.3346/jkms.2023.38.e65.

Clinical Characteristics and Outcomes of Children With SARS-CoV-2 Infection During the Delta and Omicron VariantDominant Periods in Korea

• Choi SH
• Choi JH
• Lee JK
• Eun BW
• Song SH
• Ahn B
• Kim YK
• Yun KW

• KMID: 2540123
• DOI: http://doi.org/10.3346/jkms.2023.38.e65

Abstract

Background
Data on the clinical characteristics of pediatric patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant infection are limited. We aimed to evaluate the clinical features and outcomes of children with SARS-CoV-2 infection before and after omicron variant dominance in Korea.
Methods
A multicenter retrospective cohort study was conducted in hospitalized patients aged ≤ 18 years with laboratory-confirmed SARS-CoV-2 infection at five university hospitals in South Korea. The study periods were divided into the delta (from August 23, 2021 to January 2, 2022) and omicron (from January 30 to March 31, 2022).
Results
In total, 612 hospitalized patients were identified (211, delta; 401, omicron). During the omicron and delta periods, the proportions of individuals with serious illness (moderate, severe, and critical severity) were 21.2% and 11.8%, respectively (P = 0.034). Compared with the delta period, the proportions of patients with moderate illness increased significantly in the age groups of 0–4 years (14.2% vs. 3.4%) and 5–11 years (18.6% vs. 4.2%) during the omicron period. During the two periods, the proportions of patients with complex chronic diseases (delta, 16.0% vs. 4.3%, P = 0.040; omicron, 27.1% vs. 12.7%; P= 0.002), respiratory diseases except for asthma (delta, 8.0% vs. 0.0%, P = 0.013; omicron, 9.4% vs. 1.6%; P = 0.001), and neurologic diseases (delta, 28.0% vs. 3.2%, P < 0.001; omicron, 40.0% vs. 5.1%, P < 0.001) were significantly higher in patients with serious illness than in those with nonserious illness. During the delta period, the risk for serious illness was higher among patients with obesity (adjusted odds ratio [aOR], 8.18; 95% confidence interval [CI], 2.80–27.36) and neurologic diseases (aOR, 39.43; 95% CI, 6.90–268.3) and aged 12–18 years (aOR, 3.92; 95% CI, 1.46–10.85). However, the presence of neurologic disease (aOR, 9.80; 95% CI, 4.50–22.57) was the only risk factor for serious illness during the omicron period. During the omicron period, the proportions of patients with croup (11.0% vs. 0.5%) and seizures (13.2% vs. 2.8%) increased significantly compared with the delta period.
Conclusion
Compared with the delta period, the proportions of young children and patients with complex comorbidities were higher during the omicron period in Korea. Patients

Keyword

COVID-19; SARS-CoV-2 Variants; SARS-CoV-2 Omicron Variant; SARS-CoV-2 Delta Variant; Child; Adolescent

Figure

• 

  Fig. 1 National incidence of COVID-19 and weekly distributions of study patients. The figure shows daily new confirmed COVID-19 cases per million people (7-day rolling average) in South Korea from August 22, 2021 to April 2, 2022. Nationwide population data were available from press releases by the Korea Disease Control and Prevention Agency (http://ncov.mohw.go.kr/en).3 The national incidence rate of COVID-19 (daily confirmed cases per 100,000 children) peaked during the omicron period in the week ending March 19, 2022, with 1,309.9 infected individuals aged 0–6 and 1,154.5 infected individuals aged 7–18 years. The incidence rates among children aged 0–6 and 7–18 years during the peak week in the omicron period were 72.4 and 69.1 times higher than those during the delta period.COVID-19 = coronavirus disease 2019.

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  Fig. 2 Association between the underlying medical conditions and coronavirus disease 2019 severity. (A) Distribution of illness severity according to medical complexity and the association between medical complexity and moderate or severe/critical illness during the delta period. (B) Distribution of illness severity according to medical complexity and the association between medical complexity and moderate or severe/critical illness during the omicron period.aOR = adjusted odds ratio, CI = confidence interval.

• 

  Fig. 3 Predictors of serious illness among patients with coronavirus disease 2019. (A) The delta period and (B) the omicron period.aOR = adjusted odds ratio, CI = confidence interval.

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