Publications by authors named "Ki-Wook Yun"

Background: Although there is consensus to use immunoglobulins and corticosteroids as first-line treatments for multisystem inflammatory syndrome in children (MIS-C), the effectiveness of biological immunomodulators in patients refractory to standard therapy remains unclear. We aimed to outline real-world data on biological immunomodulators.

Method: A literature search using Ovid-Medline, EMBASE, Cochrane CDSR, and KMBASE was conducted from September 2021 to August 2022; certainty of evidence was assessed via GRADE.

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  • - This study focused on community-acquired pneumonia (CAP) in children, aiming to identify mucosal biomarkers that can aid in determining the severity and cause of the illness.
  • - Researchers analyzed cytokine levels in nasopharyngeal samples from 182 children with CAP and 26 healthy controls, finding that those with atypical bacteria and influenza virus had significantly elevated cytokine concentrations compared to those with typical bacteria.
  • - The findings suggest that differences in inflammatory and antiviral cytokine levels correlate with disease severity in CAP, indicating that mucosal biomarkers might be helpful for better assessing and classifying the condition in pediatric patients.
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  • A resurgence of Mycoplasma pneumoniae (MP) infections, mainly causing pneumonia in kids, was noted after the COVID-19 pandemic, leading to a study on its clinical features and treatment in late 2023.
  • Out of 474 patients screened, 374 met criteria for MP pneumonia, with most presenting fever and a common radiological sign being lobar consolidation, while macrolide resistance was high at 87%.
  • The study underscores the challenge of treating MP pneumonia due to high macrolide resistance rates, as these antibiotics, along with corticosteroids, are still frequently used despite their ineffectiveness in improving radiological outcomes.
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  • The study investigates antibiotic resistance in Acinetobacter baumannii (AB) and non-baumannii Acinetobacter complex (NB-ACB) in invasive infections among Korean children.
  • A total of 67 isolates were collected, with a high percentage of AB (73.1%) demonstrating significant multi-drug resistance, especially within the clonal complex 92.
  • The research emphasizes the necessity for continued monitoring and analysis of resistance genes to effectively manage drug-resistant infections, particularly those involving CC92 AB.
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  • The COVID-19 pandemic led to a significant decline in the incidence of various respiratory viruses due to health measures, but these infections returned as restrictions were lifted, particularly in Korean children.
  • A nationwide surveillance study analyzed respiratory virus data from children and adolescents from January 2017 to June 2023, comparing detection rates and age distributions before and after the pandemic.
  • Findings showed a drop in overall virus detection during the pandemic, with a notable increase in co-detections post-pandemic; unique outbreaks of certain viruses like PIV and HMPV occurred out of season, and the average age of affected children increased significantly in 2023 compared to pre-pandemic years.
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  • * A significant portion of the cases were in very young children, particularly those under 3 months (20.9%) and under 2 years (54.5%), with pneumonia and bronchiolitis affecting 40.9% and 23.8%, respectively.
  • * Severity of RSV infection was linked to nasopharyngeal colonization and existing health conditions, highlighting the serious impact of RSV on infants and toddlers, even those without pre-existing issues.
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  • This study focused on the causes and clinical features of community-acquired pneumonia (CAP) in children in Korea, analyzing data from 2015 to 2020, before the COVID-19 pandemic.
  • Researchers reviewed 2,864 suspected CAP cases, ultimately identifying 517 confirmed cases, with notable symptoms including high fever (59.4%) and dyspnea (19.9%), and nearly a third requiring respiratory support.
  • Pathogens were identified in about half of the cases, with viruses being the most common culprits, particularly adenovirus and respiratory syncytial virus (RSV), while a small percentage faced severe outcomes, including fatalities.
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  • Enterovirus D68 (EV-D68) is a virus that can cause respiratory infections and has been linked to neurological issues, but it had not been reported in Korea until this study.
  • The study successfully identified three strains of EV-D68 in Korean children with respiratory symptoms during late 2022, using a specialized in-house mRT-PCR kit.
  • Phylogenetic analysis indicated that the detected strains belong to subclade B3 and are more closely related to European EV-D68 strains than those from Japan, marking a significant finding in the understanding of this virus's presence in Korea.
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Vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been acknowledged as an effective mean of preventing infection and hospitalization. However, the emergence of highly transmissible SARS-CoV-2 variants of concern (VOCs) has led to substantial increase in infections among children and adolescents. Vaccine-induced immunity and longevity have not been well defined in this population.

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Pneumonia is a common pediatric infectious disease that is familiar to pediatricians and a major cause of hospitalization worldwide. Recent well-designed epidemiologic studies in developed countries indicated that respiratory viruses are detected in 30%-70%, atypical bacteria in 7%-17%, and pyogenic bacteria in 2%-8% of children hospitalized with community-acquired pneumonia (CAP). The etiological distribution of CAP varies widely by child age and the epidemiological season of the respiratory pathogen.

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Background: In Korea, during the early phase of the coronavirus disease 2019 (COVID-19) pandemic, we responded to the uncertainty of treatments under various conditions, consistently playing catch up with the speed of evidence updates. Therefore, there was high demand for national-level evidence-based clinical practice guidelines for clinicians in a timely manner. We developed evidence-based and updated living recommendations for clinicians through a transparent development process and multidisciplinary expert collaboration.

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  • Acinetobacter baumannii has become a significant threat for critically ill children, particularly in invasive infections, with a high 30-day mortality rate linked to this pathogen.
  • A study conducted from 2001 to 2020 on isolates from children revealed a complete shift in genotypes towards the more resistant CC92 genotype after 2010.
  • The CC92 genotype exhibited extremely high rates of carbapenem resistance (94.2%), and colistin resistance rose significantly between 2014-2017, highlighting the urgent need for ongoing surveillance and treatment strategies.
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  • Respiratory syncytial virus (RSV) is a major cause of respiratory infections, particularly affecting infants under 2 years old and the elderly, leading to many hospitalizations.* -
  • The review focuses on RSV's impact in Korea, emphasizing the need for effective vaccines to alleviate the health burden on vulnerable groups.* -
  • Advancements in understanding immune responses and vaccine technology are crucial for developing safe and effective vaccines against RSV to reduce illness and long-term health issues like asthma.*
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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.

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Although much interest has emerged regarding post-COVID conditions, data on children and adolescents are limited. The prevalence of long COVID and common symptoms were analyzed in this case-control study of 274 children. Prolonged non-neuropsychiatric symptoms were more frequent in the case group (17.

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  • As of September 3, 2022, Korea reported over 5.3 million COVID-19 cases in children under 18, with a case fatality rate of 0.85 per 100,000.
  • Of the 46 deaths, most were boys, with a median age of 7, and nearly half had underlying health conditions, particularly neurologic diseases.
  • COVID-19 deaths often occurred quickly after diagnosis, highlighting the need for improved access to medical care for children during the pandemic.
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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.

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There are few data about pneumonia (PCP) in children, particularly in developed countries. This study investigated the clinical characteristics and prognosis of the clinical PCP in non-HIV-infected Korean children. Children with positive results for the staining and/or polymerase chain reaction (PCR) for between 2001 and 2021 were identified.

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Omicron, a recent variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is currently globally dominating. We reviewed the etiology and epidemiology of croup over an approximately 5-year period, with an emphasis on the recent dominance of the Omicron variant. Children less than 5 years of age seen in the emergency department with diagnosis of croup from two large national tertiary hospitals were collected for the period from January 2018 through March 2022.

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Long-lasting coronavirus disease 2019 (COVID-19) symptoms beyond 12 weeks, the so-called 'long COVID' have been increasingly reported worldwide. Long COVID can be manifested in various forms, and there is an increasing demand for proper assessment and management. However, it is challenging when trying to determine the best-practice standards of care based on the current evidence because there is no internationally agreed clinical definition or clear treatment pathway.

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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern have been emerging. However, knowledge of temporal and spatial dynamics of SARS-CoV-2 is limited. This study characterized SARS-CoV-2 evolution in immunosuppressed patients with long-term SARS-CoV-2 shedding for 73-250 days, without specific treatment.

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Background: Parainfluenza virus type 3 (PIV3) and respiratory syncytial virus (RSV) B epidemics occurred in South Korea in late 2021. We investigated epidemiological changes of PIV3 and RSV B infections in Korean children before and during the coronavirus disease 2019 (COVID-19) pandemic.

Methods: In this multicenter retrospective study, we enrolled patients aged less than 19 years with PIV3 or RSV infection in four university hospitals from January 2018 to January 2022.

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Coronavirus disease 2019 (COVID-19) is a mild to moderate respiratory illness in most children and adolescents, but a small proportion develop severe or critical illness. Although pediatric clinical trials for the treatment of COVID-19 are sparse, there are some available drugs for children and adolescents with severe COVID-19. This review summarizes clinical data focusing on antiviral agents and immunomodulators for COVID-19 treatment.

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