Twenty-Five Year Trend Change in the Etiology of Pediatric Invasive Bacterial Infections in Korea, 1996–2020

Background The coronavirus disease-2019 (COVID-19) pandemic has contributed to the change in the epidemiology of many infectious diseases. This study aimed to establish the pre-pandemic epidemiology of pediatric invasive bacterial infection (IBI). Methods A retrospective multicenter-based surveillance for pediatric IBIs has been maintained from 1996 to 2020 in Korea. IBIs caused by eight bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pyogenes, Listeria monocytogenes, and Salmonella species) in immunocompetent children > 3 months of age were collected at 29 centers. The annual trend in the proportion of IBIs by each pathogen was analyzed. Results A total of 2,195 episodes were identified during the 25-year period between 1996 and 2020. S. pneumoniae (42.4%), S. aureus (22.1%), and Salmonella species (21.0%) were common in children 3 to 59 months of age. In children ≥ 5 years of age, S. aureus (58.1%), followed by Salmonella species (14.8%) and S. pneumoniae (12.2%) were common. Excluding the year 2020, there was a trend toward a decrease in the relative proportions of S. pneumoniae (rs = −0.430, P = 0.036), H. influenzae (rs = −0.922, P < 0.001), while trend toward an increase in the relative proportion of S. aureus (rs = 0.850, P < 0.001), S. agalactiae (rs = 0.615, P = 0.001), and S. pyogenes (rs = 0.554, P = 0.005). Conclusion In the proportion of IBIs over a 24-year period between 1996 and 2019, we observed a decreasing trend for S. pneumoniae and H. influenzae and an increasing trend for S. aureus, S. agalactiae, and S. pyogenes in children > 3 months of age. These findings can be used as the baseline data to navigate the trend in the epidemiology of pediatric IBI in the post COVID-19 era. Graphical

Twenty-Five Year Trend Change in the Etiology of Pediatric Invasive Bacterial Infections in Korea, 1996-2020.

BACKGROUND: The coronavirus disease-2019 (COVID-19) pandemic has contributed to the change in the epidemiology of many infectious diseases. This study aimed to establish the pre-pandemic epidemiology of pediatric invasive bacterial infection (IBI). METHODS: A retrospective multicenter-based surveillance for pediatric IBIs has been maintained from 1996 to 2020 in Korea. IBIs caused by eight bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pyogenes, Listeria monocytogenes, and Salmonella species) in immunocompetent children > 3 months of age were collected at 29 centers. The annual trend in the proportion of IBIs by each pathogen was analyzed. RESULTS: A total of 2,195 episodes were identified during the 25-year period between 1996 and 2020. S. pneumoniae (42.4%), S. aureus (22.1%), and Salmonella species (21.0%) were common in children 3 to 59 months of age. In children ≥ 5 years of age, S. aureus (58.1%), followed by Salmonella species (14.8%) and S. pneumoniae (12.2%) were common. Excluding the year 2020, there was a trend toward a decrease in the relative proportions of S. pneumoniae (rs = -0.430, P = 0.036), H. influenzae (rs = -0.922, P < 0.001), while trend toward an increase in the relative proportion of S. aureus (rs = 0.850, P < 0.001), S. agalactiae (rs = 0.615, P = 0.001), and S. pyogenes (rs = 0.554, P = 0.005). CONCLUSION: In the proportion of IBIs over a 24-year period between 1996 and 2019, we observed a decreasing trend for S. pneumoniae and H. influenzae and an increasing trend for S. aureus, S. agalactiae, and S. pyogenes in children > 3 months of age. These findings can be used as the baseline data to navigate the trend in the epidemiology of pediatric IBI in the post COVID-19 era.

Deciphering changes in the incidence of the Guillain-Barré syndrome during the COVID-19 pandemic: a nationwide time-series correlation study.

Background: Postinfectious autoimmunity is a hallmark of Guillain-Barré syndrome (GBS), and GBS incidence closely parallels that of its immune triggers. Sociobehavioural interventions implemented during the COVID-19 pandemic have altered the infectious disease landscape. Methods: This nationwide time-series correlation study analysed GBS incidence, sentinel surveillance and SARS-CoV-2 vaccination data from January 2017 to December 2021 in the National Health Insurance Service and Korean Disease Control and Prevention Agency databases. The incidence of GBS and sentinel gastrointestinal and respiratory infectious diseases during the pandemic (2020-2021) was estimated and compared with both prepandemic (2017-2019) and incidence predicted in a time-series forecasting model. Time-series correlation analysis was used to examine the temporal association between GBS, infectious triggers and SARS-CoV-2 vaccination. Results: During the pandemic, the total crude cumulative incidence rate was 2.1 per 100 000 population, which is lower than the prepandemic incidence, especially in age groups of less than 60 years. Seasonality was briefly interrupted during the winter of 2021. The majority of respiratory and some gastrointestinal conditions had a lower-than-expected incidence during the pandemic. Compared with the prepandemic state, during the pandemic period a higher number of gastrointestinal pathogens (Escherichia coli, Campylobacter spp., Clostridium perfringens, Yersinia enterocolitica and enteric adenovirus) had significant, moderate-to-strong positive temporal associations with GBS. The temporal association between SARS-CoV-2 infection and GBS was not significant, but SARS-CoV-2 vaccination exhibited a strong positive temporal association with GBS in 2021. Conclusion: The incidence of GBS and sentinel infectious diseases decreased to below-expected levels during the pandemic, with the former attributable to the decreased incidence of non-COVID-19 respiratory and gastrointestinal infections. The evolving incidence of autoimmune postinfectious phenomena following the pandemic needs attention.

Parental concerns about COVID-19 vaccine safety and hesitancy in Korea: implications for vaccine communication.

OBJECTIVES: Vaccination is one of the most important strategies to contain the spread of coronavirus disease 2019 (COVID-19). Vaccination in children is dependent on their parents, making it important to understand parents' awareness and attitudes toward vaccines in order to devise strategies to raise vaccination rates in children. METHODS: A web-based nationwide survey was conducted among Korean parents of 7-year-old to 18-year-old children in August 2021 to estimate parents' intention to vaccinate their children against COVID-19 and identify key factors affecting parental acceptance and hesitancy through regression analysis. RESULTS: Approximately 56.4% (575/1,019) were willing to vaccinate their children against COVID-19. Contributing factors to COVID-19 vaccine hesitancy were being a mother (adjusted odds ratio [aOR], 0.36; 95% confidence interval [CI], 0.25 to 0.52), a lower education level (aOR, 0.83; 95% CI, 0.70 to 0.97), hesitancy to other childhood vaccines (aOR, 0.78; 95% CI, 0.64 to 0.96), and refusal to vaccinate themselves (aOR, 0.08; 95% CI, 0.02 to 0.20). Having older children (aOR, 1.20; 95% CI, 1.13 to 1.28), trusting the child's doctor (aOR, 1.19; 95% CI, 1.07 to 1.32), positive perceptions of the COVID-19 vaccine's effectiveness (aOR, 2.60; 95% CI, 1.90 to 3.57) and perceiving the COVID-19 vaccine as low-risk (aOR, 1.68; 95% CI, 1.27 to 2.24) were associated with COVID-19 vaccine acceptance. Concerns about adverse reactions were the most common cause of hesitancy. CONCLUSIONS: Providing parents with accurate and reliable information on vaccine effectiveness and safety is important to increase COVID-19 vaccine uptake in children. Differential or targeted approaches to parents according to gender, age, and their children's age are necessary for effective communication about vaccination in children.

Pediatric Deaths Associated With Coronavirus Disease 2019 (COVID-19) in Korea.

As of September 3, 2022, 5,388,338 coronavirus disease 2019 (COVID-19) cases and 46 deaths (3 in 2021 and 43 in 2022) were reported in children ≤ 18 years in Korea. Cumulative confirmed cases accounted for 67.3% of the population aged ≤ 18 years and case fatality rate was 0.85/100,000. Among 46 fatal cases, 58.7% were male and median age was 7 years. Underlying diseases were present in 47.8%; neurologic diseases (63.6%) and malignancy (13.6%) most common. Only four had history of COVID-19 immunization. COVID-19 associated deaths occurred at median 2 days from diagnosis (range: -1 to 21). Among COVID-19 deaths, 41.3% occurred before admission; 2 before hospital arrival and 17 in the emergency department. Among children whose cause was documented, myocarditis, respiratory and multiorgan failure were most common. COVID-19 associated death was seen early after diagnosis in children and public health policies to provide access to medical care for children with COVID-19 are essential during the pandemic.

Case report: Myocarditis with nonsustained ventricular tachycardia following COVID-19 mRNA vaccination in a female adolescent

Children with underlying medical conditions potentially develop severe illness from Coronavirus disease 2019 (COVID-19). The use of vaccines against COVID-19 is currently recommended for the pediatric population. The COVID-19 vaccine has a temporal association with the occurrence of myocarditis. Although most patients with COVID-19 vaccination-associated myocarditis (C-VAM) exhibit a mild clinical course and rapid recovery, C-VAM potentially causes electrical instability and sudden cardiac death. Herein, we report the case of a 17-year-old woman who presented with chest pain and syncope following the first dose of the messenger RNA COVID-19 vaccine. The patient's heart function was impaired, and nonsustained ventricular tachycardia was frequent. Cardiac magnetic resonance (CMR) imaging satisfied the criteria for myocarditis. Despite the administration of immunomodulatory drugs, the patient's heart function was not fully restored, and the concentration of cardiac enzymes remained above the normal range. Persistence of late gadolinium enhancement was observed on short-term follow-up CMR imaging. Although most patients with C-VAM exhibit mild symptoms, significant cardiac arrhythmias potentially occur. Furthermore, some patients with C-VAM demonstrate prolonged impaired heart function and sustained late gadolinium enhancement on follow-up CMR imaging. Therefore, monitoring of electrical and functional cardiac abnormalities in patients with C-VAM is crucial and the long-term outcomes and prognosis of patients with C-VAM require further investigation.

Parental Acceptance of COVID-19 Vaccination for Children and Its Association With Information Sufficiency and Credibility in South Korea.

Importance: Vaccination against COVID-19 is an effective method for individuals to reduce negative health outcomes. However, widespread COVID-19 vaccination among children has been challenging owing to parental hesitancy. Objective: To examine parental decision-making in favor of the COVID-19 vaccine for their children and its association with the sufficiency and credibility of the information about the vaccine. Design, Setting, and Participants: This cross-sectional survey study was conducted in South Korea from February 7 to 10, 2022, 7 weeks before initiation of the COVID-19 vaccine for children aged 5 to 11 years. Parents were included if they spoke Korean and had at least 1 child in elementary school (grades 1-6). Parents and children were included in a 1:1 ratio; a total of 113 450 parents and 113 450 children were included in the analysis. Statistical analysis was performed between March and April 2022. Main Outcomes and Measures: The main outcomes of interest were (1) parental acceptance of COVID-19 vaccination for their children and (2) its association with self-reported sufficiency and credibility of information about the vaccine. A multivariable logistic regression was used to evaluate factors associated with parental decision-making in favor of COVID-19 vaccination; path analysis was used to examine indirect effects of information sufficiency and credibility. Results: Of the 113 450 children, 58 342 (51.4%) were boys, and the mean (SD) age was 10.1 (1.5) years. Of the 113 450 parents who responded, 7379 (6.5%) were accepting vaccination for their children; 15 731 (13.9%) reported the vaccine-related information they received was sufficient, and 23 021 (20.3%) reported the information was credible. Parents who reported that the information was sufficient were 3.08 times (95% CI, 2.85-3.33; P < .001) more likely to report being willing to vaccinate their children than those who believed the information was insufficient, and those who reported that the information was credible were 7.55 times (95% CI, 6.46-8.87; P < .001) more likely to report being willing to vaccinate their children than those who believed the information was not credible. Higher levels of information sufficiency and credibility were associated with perceptions of increased vaccine safety (sufficiency: ß = 0.08; P < .001; credibility: ß = 0.59; P < .001) and effectiveness (sufficiency: ß = 0.05; P < .001; credibility: ß = 0.60; P < .001). Conclusions and Relevance: In this study, a significant association was found between self-reported sufficiency and credibility of vaccine-related information and parental decision-making regarding COVID-19 vaccination for their children, suggesting that communications and policies that provide sound information are essential to improve vaccination rates.

Spatial distribution of SARS-CoV-2 infection in schools, South Korea.

Identification of geographical areas with high burden of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission in schools using spatial analyses has become an important tool to guide targeted interventions in educational setting. In this study, we aimed to explore the spatial distribution and determinants of coronavirus disease 2019 (COVID-19) among students aged 3-18 years in South Korea. We analysed the nationwide epidemiological data on laboratory-confirmed COVID-19 cases in schools and in the communities between January 2020 and October 2021 in South Korea. To explore the spatial distribution, the global Moran's I and Getis-Ord's G using incidence rates among the districts of aged 3-18 years and 30-59 years. Spatial regression analysis was performed to find sociodemographic predictors of the COVID-19 attack rate in schools and in the communities. The global spatial correlation estimated by Moran's I was 0.647 for the community population and 0.350 for the student population, suggesting that the students were spatially less correlated than the community-level outbreak of SARS-CoV-2. In schools, attack rate of adults aged 30-59 years in the community was associated with increased risk of transmission (P < 0.0001). Number of students per class (in kindergartens, primary schools, middle schools and high schools) did not show significant association with the school transmission of SARS-CoV-2. In South Korea, COVID-19 in students had spatial variations across the country. Statistically significant high hotspots of SARS-CoV-2 transmission among students were found in the capital area, with dense population level and high COVID-19 burden among adults aged 30-59 years. Our finding suggests that controlling community-level burden of COVID-19 can help in preventing SARS-CoV-2 infection in school-aged children.

SARS-CoV-2-Naïve Korean Children and Adolescents Hospitalized With COVID-19 in 2021.

BACKGROUND: The risk of severe outcomes with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) delta variant remains low in children and adolescents, but less is known about its effect on the SARS-CoV-2-naïve population. This study evaluated clinical manifestations and risk factors for moderate-to-critical coronavirus disease 2019 (COVID-19) in mostly SARS-CoV-2-naïve children and adolescents in 2021. METHODS: This multicenter retrospective study included patients aged 0-18 years who were hospitalized with COVID-19 at 8 referring hospitals in South Korea during the predelta-predominant and delta-predominant periods in 2021. Each case was labeled as either hospitalization with medical needs or for isolation. Severity was categorized as mild, moderate, severe, or critical with regard to pneumonia presence and illness severity. RESULTS: Among 753 cases, most (99.5%) had no prior history of COVID-19 or vaccination against COVID-19. The proportions of hospitalization with medical needs (3.5% vs. 19.7%), moderate illness (0.9% vs. 4.0%), and severe/critical illness (0.8% vs. 5.3%) increased during delta predominance. The risk of moderate-to-critical COVID-19 among hospitalizations with medical needs was higher among patients aged 12-18 years (adjusted odds ratio [aOR], 4.1; 95% confidence interval [CI], 1.5-11.8) and with obesity (aOR, 6.9; 95% CI, 2.4-19.6) but not among patients infected during delta predominance. However, children with obesity experienced more severe COVID-19 during delta predominance (aOR, 6.1; 95% CI, 1.2-29.6). CONCLUSION: Despite its similar severity among most SARS-CoV-2-naïve children and adolescents, the delta variant may affect COVID-19 severity in those with high-risk underlying medical conditions. Underlying conditions, particularly obesity, may cause severe COVID-19 in children and adolescents, warranting strong consideration for vaccinating high-risk children.

Diagnostic Performance, Stability, and Usability of Self-Collected Combo Swabs and Saliva for Coronavirus Disease 2019 Diagnosis: A Case-Control Study.

BACKGROUND: Self-sampling procedures to detect severe acute respiratory syndrome coronavirus 2 is important for patients who have difficulty visiting the hospital and may decrease the burden for health care workers (HCWs). The objective of this study was to evaluate the diagnostic performance, stability and usability of self-collected nasal and oral combo swabs and saliva specimens. MATERIALS AND METHODS: We conducted a case-control study with 50 patients with coronavirus disease 2019 (COVID-19) and 50 healthy volunteers from March, 2021 to June, 2021. We performed real-time reverse-transcription polymerase chain reaction to compare the diagnostic performance of self-collected specimens using positive percent agreements (PPAs). RESULTS: The PPAs between self-collected and HCW-collected specimens were 77.3 - 81.0% and 80.5 -86.7% for the combo swabs and saliva specimens, respectively. The PPAs increased to 88.9 - 89.2% and 81.2 - 82.1% with a cycle threshold value ≤30. CONCLUSION: The diagnostic performance of self sampling was comparable to that of HCW sampling in patients with high viral loads and may thus assist in the early diagnosis of COVID-19.

A Study on the COVID-19 Preventive Behaviors of Automobile Manufacturing Workers in South Korea.

The present study used a cross-sectional, descriptive survey design to investigate the influencing factors of COVID-19-related infection prevention behaviors of workers in the automobile manufacturing sector. An online survey was conducted on 157 workers in the automobile manufacturing sector of a company in Korea. We analyzed the collected data using SPSS to test whether there were significant differences in COVID-19 risk perception, crisis communication, health literacy, and infection prevention behaviors according to the general characteristics of the participants. An independent sample t-test and a one-way analysis of variance (ANOVA) were performed. A Pearson's correlation analysis was performed to identify the correlations among COVID-19 risk perception, crisis communication, health literacy, and infection prevention behaviors. Multiple regression analysis was performed to identify the influencing factors of COVID-19 infection prevention behaviors. The regression model was found to be significant, and the employment period at current job, COVID-19 prevention education, source of information, COVID-19 risk perception, crisis communication, and health literacy were also found to be significant. Among the demographic variables, employment period at current job of 5-10 years showed a higher level of infection prevention behaviors than that of <5 years. Moreover, the level of infection prevention behaviors was also significantly higher when COVID-19-related information was acquired through the KDCA/health center. Higher COVID-19 risk perception, crisis communication, and health literacy were associated with significantly higher levels of infection prevention behaviors. Therefore, based on the results, health managers need to develop programs and educate and improve information comprehension and crisis communication skills in order to promote workers' infection prevention behaviors of emerging infectious diseases in an era of global change.

Attitude and Acceptance of COVID-19 Vaccine in Parents and Adolescents: A Nationwide Survey.

PURPOSE: Coronavirus disease 2019 (COVID-19) vaccines are currently authorized for emergency use in adolescents aged 12-17 years; however, there is concern and uncertainty regarding the safety and necessity of COVID-19 vaccination. A survey was carried out to assess the attitudes and acceptance towards vaccination in adolescents. METHODS: A nationwide web-based survey was conducted among adolescents aged 12-17 years and their parents between June 29 and July 8, 2021 on a platform provided by the Ministry of Education. RESULTS: A total of 341,326 parents and 272,914 adolescents participated in this study. Intention for vaccination was 69.1% for adolescents, and 72.2% of parents reported they would recommend vaccination for their child. Among adolescents, perception of safety (odds ratio [OR] 4.09, 95% confidence interval [CI] 3.95-4.22), effectiveness (OR 2.24, 95% CI 2.17-2.32), and risk-benefit (OR 1.75, 95% CI 1.72-1.78) had the highest impact on intention for vaccination. Also, perceived risk (OR 1.14, 95% CI 1.12-1.17), severity (OR 1.12, 95% CI 1.10-1.13) for COVID-19 infection, self-health perception (OR 1.12, 95%, CI 1.10-1.14) and recent vaccination of childhood vaccines (OR 1.25, 95% CI 1.19-1.32) were related to intention for COVID-19 vaccination. On the other hand, self-perceived knowledge (OR 0.96, 95% 0.95-0.98) was related to vaccine hesitancy. Gender or school district did not influence intention for COVID-19 vaccination in adolescents. DISCUSSION: Decisions on COVID-19 vaccination for adolescents should be a shared process between adolescents, parents, and physicians based on updated information on safety and effectiveness.

Short Term Impact of Coronavirus Disease 2019 Vaccination in Children in Korea.

BACKGROUND: The epidemiology of coronavirus disease 2019 (COVID-19) has changed continuously throughout the pandemic. METHODS: We analyzed changes in the incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection according to the age group in South Korea from February 2020 to December 2021. RESULTS: Since the COVID-19 pandemic, the incidence among adults aged ≥ 18 years was higher than all the other age groups in 2020; however, a shift toward younger ages occurred in June 2021. In addition, we found significant changes in epidemiology after the introduction of SARS-CoV-2 vaccines in adults aged ≥ 18 and children 12-17 years. Until recently, children were not regarded as the drive for the pandemic; however, children aged 5-11 and 0-4 years had the highest incidence among all the age groups. CONCLUSION: Therefore, policies for clinical support for an increase in COVID-19 cases among young children and age-specific preventive measures are needed.

Antibody Responses to SARS-CoV-2 in Children With COVID-19.

BACKGROUND: The immunologic features of children with coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are not clearly delineated. This study was conducted to evaluate SARS-CoV-2-specific antibody responses in children with COVID-19. METHODS: The levels of anti-spike (S) IgG, anti-SARS-CoV-2 IgG, and neutralizing antibody (NAb) were measured during various time points in children <19 years of age with COVID-19 in South Korea from February 2020 to September 2020. RESULTS: One hundred sixty-five blood samples from 114 children with COVID-19 (43.9% asymptomatic and 56.1% mildly symptomatic) were analyzed. In both asymptomatic and mildly symptomatic children, the positive rates of anti-S IgG, anti-SARS-CoV-2 IgG, and NAb were low within 7 days after onset, but they soon reached 100% 14 to <28 days after onset. In symptomatic children, the geometric mean titers (GMTs) of antibodies were all below the positive cutoff during the first 2 weeks from onset and peaked at 28 to <56 days (5.6 for anti-S IgG, 383.6 for anti-SARS-CoV-2 IgG, and 55.0 for NAb, P < .001, respectively). Antibody levels remained detectable up to 3 months after infection. The antibody GMTs during the period 14 to <56 days after symptom onset were highest in children aged 0-4 years. CONCLUSIONS: These results collectively present the humoral immune responses during SARS-CoV-2 infection in children. A further longitudinal study is needed to thoroughly understand the immune system and for effective vaccine development in children during the COVID-19 pandemic.

Differential Impact of Nonpharmaceutical Interventions on the Epidemiology of Invasive Bacterial Infections in Children During the Coronavirus Disease 2019 Pandemic.

BACKGROUND: Invasive bacterial infection (IBI) remains a major burden of mortality and morbidity in children. As coronavirus disease 2019 (COVID-19) emerged, stringent nonpharmaceutical interventions (NPIs) were applied worldwide. This study aimed to evaluate the impact of NPIs on pediatric IBI in Korea. METHODS: From January 2018 to December 2020, surveillance for pediatric IBIs caused by 9 pathogens (S. pneumoniae, H. influenzae, N. meningitidis, S. agalactiae, S. pyogenes, S. aureus, Salmonella species, L. monocytogenes and E. coli) was performed at 22 hospitals throughout Korea. Annual incidence rates were compared before and after the COVID-19 pandemic. RESULTS: A total of 651 cases were identified and the annual incidence was 194.0 cases per 100,000 in-patients in 2018, 170.0 in 2019 and 172.4 in 2020. Most common pathogen by age group was S. agalactiae in infants < 3 months (n = 129, 46.7%), S. aureus in 3 to < 24 months (n = 35, 37.2%), Salmonella spp. in 24 to < 60 months (n = 24, 34.8%) and S. aureus in children ≥ 5 years (n = 128, 60.7%). Compared with 2018 to 2019, the incidence rate in 2020 decreased by 57% for invasive pneumococcal disease (26.6 vs. 11.5 per 100,000 in-patients, P = 0.014) and 59% for Salmonella spp. infection (22.8 vs. 9.4 per 100,000 in-patients, P = 0.018). In contrast, no significant changes were observed in invasive infections due to S. aureus, S. agalactiae and E. coli. CONCLUSIONS: The NPIs implemented during the COVID-19 pandemic reduced invasive diseases caused by S. pneumoniae and Salmonella spp. but not S. aureus, S. agalactiae and E. coli in children.

Analysis of Critical COVID-19 Cases Among Children in Korea.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is generally asymptomatic or mild in otherwise healthy children, however, severe cases may occur. In this study, we report the clinical characteristics of children classified as critical COVID-19 in Korea to provide further insights into risk factors and management in children. METHODS: This study was a retrospective case series of children < 18 years of age classified as critical COVID-19. Cases were identified by the Korea Disease Control and Prevention Agency surveillance system and medical records were reviewed. Critical COVID-19 was defined as cases with severe illness requiring noninvasive (high flow nasal cannula, continuous positive airway pressure, or bilevel positive airway pressure) or invasive mechanical ventilation, extracorporeal membrane oxygenation (ECMO) or continuous renal replacement therapy (CRRT), between January 20, 2020 and October 7, 2021. RESULTS: Among 39,146 cases diagnosed with COVID-19 in subjects < 18 years of age, eight cases (0.02%) were identified as critical COVID-19. The median age was 13 years (range 10 month-17 years) and male-to-female ratio was 1:1. Three children had underlying diseases; one child has asthma and major depressive disorder, one child had Lennox-Gastaut syndrome and one child had mental retardation and was newly diagnosed with type 2 diabetes mellitus with the diagnosis of COVID-19. Among the eight children, seven were obese (body mass index range [BMI] median 29.3, range 25.9-38.2, weight-for-length > 97% for infant) and one was overweight (BMI 21.3). All patients had fever, six patients had dyspnea or cough and other accompanied symptoms included sore throat, headache, lethargy and myalgia. Radiologic findings showed pneumonia within 1-8 days after symptom onset. Pneumonia progressed in these children for 2-6 days and was improved within 5-32 days after diagnosis. Among the eight critical cases, remdesivir was administered in six cases. Steroids were provided for all cases. Inotropics were administered in one case. Six cases were treated with noninvasive mechanical ventilator and three required mechanical ventilator. One case required ECMO due to acute respiratory distress syndrome. All cases were admitted to the intensive care unit and admission period ranged from 9-39 days. Among all critical COVID-19 cases < 18 years of age, there were no fatal cases. CONCLUSION: To develop appropriate policies for children in the COVID-19 pandemic, it is important to monitor and assess the clinical burden in this population.