Epidemiology of Respiratory Viruses in Korean Children Before and After the COVID-19 Pandemic: A Prospective Study From National Surveillance System.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic led to a decrease in the seasonal incidence of many respiratory viruses worldwide due to the impact of nonpharmaceutical interventions (NPIs). However, as NPI measures were relaxed, respiratory viral infections re-emerged. We aimed to characterize the epidemiology of respiratory viruses in Korean children during post-COVID-19 pandemic years compared to that before the pandemic. METHODS: A nationwide prospective ongoing surveillance study has been conducted for detection of respiratory viruses between January 2017 and June 2023. We included data on adenovirus (AdV), human bocavirus (HBoV), human coronavirus (HCoV), human metapneumovirus (HMPV), human rhinovirus (HRV), influenza virus (IFV), parainfluenza virus (PIV), and respiratory syncytial virus (RSV), which were detected in children and adolescents younger than 20 years. We analyzed the weekly detection frequency of individual viruses and the age distribution of the affected children. The study period was divided into prepandemic (2017-2019) and postpandemic (2021-2023) periods. RESULTS: A total of 19,589 and 14,068 samples were collected in the pre- and postpandemic periods, respectively. The overall detection rate of any virus throughout the study period was 63.1%, with the lowest occurring in the 2nd half of 2020 (50.6%) and the highest occurring in the 2nd half of 2021 (72.3%). Enveloped viruses (HCoV, HMPV, IFV, PIV, and RSV) almost disappeared, but nonenveloped viruses (AdV, HBoV, and HRV) were detected even during the peak of the COVID-19 pandemic. The codetection rate increased from 15.0% prepandemic to 19.1% postpandemic (P < 0.001). During the postpandemic period, a large out-of-season PIV and HMPV epidemic occurred, but the usual seasonality began to be restored in 2023. The mean age of children with each virus detected in 2023 was significantly greater than that in prepandemic years (P = 0.003 and 0.007 for AdV and HCoV, respectively; P < 0.001 for others). The mean age of children with IFV increased in 2022 (11.1 ± 5.2 years) from prepandemic years (7.9 ± 4.6 years) but decreased to 8.7 ± 4.1 years in 2023. CONCLUSION: With the relaxation of NPI measures, several seasonal respiratory viruses cocirculated with unusual seasonal epidemic patterns and were associated with increasing age of infected children.

Expert Consensus on the Structure, Role, and Procedures of the Korea Expert Committee on Immunization Practices.

BACKGROUND: The Korea Expert Committee on Immunization Practices (KECIP) is a key advisory body the government to develop guidelines and provide technical advisory activities on immunization policies in Korea. A recent policy study, inspired by global best practices, aims to enhance KECIP's functionality for providing timely and transparent recommendations in the face of evolving vaccine science and emerging infectious diseases like COVID-19. METHODS: This study reviewed the current status of KECIP and collected expert opinions through surveys and consultations. Among the 40 panel members who were surveyed, 19 responded to a questionnaire specifically designed to assess the potential areas of improvement within KECIP. RESULTS: The majority of respondents favored maintaining the current member count and emphasized the need for a subcommittee. Opinions varied on issues such as the length of KECIP's term, the representation of vaccine manufacturers' perspectives, and the chairperson's role. However, there was a consensus on the importance of expertise, transparency, and fair proceedings within the committee. CONCLUSION: This study underscores the pivotal role of KECIP in shaping national immunization policies, emphasizing the necessity for informed guidance amidst evolving vaccine science and emerging infectious diseases. Furthermore, it stressed the importance of enhancing KECIP's capacity to effectively address evolving public health challenges and maintain successful immunization programs in South Korea.

Molecular epidemiology of Acinetobacter baumannii complex causing invasive infections in Korean children during 2001-2020.

BACKGROUND: Acinetobacter baumannii (AB) has emerged as one of the most problematic pathogens affecting critically ill patients. This study aimed to investigate the longitudinal epidemiology of AB causing invasive diseases in children. METHODS: Acinetobacter spp. cultured from sterile body fluids and identified as Acinetobacter calcoaceticus-baumannii (ACB) complexes by automated systems from children aged below 19 years old were prospectively collected during 2001-2020. The discriminative partial sequence of rpoB gene was sequenced to identify the species, and sequence types (STs) were determined. Temporal changes in antimicrobial susceptibilities and STs were analyzed. RESULTS: In total, 108 non-duplicate ACB isolates were obtained from patients with invasive infections. The median age was 1.4 (interquartile range, 0.1-7.9) years, and 60.2% (n = 65) were male. Acinetobacter baumannii comprised 55.6% (n = 60) of the isolates, and the 30-day mortality was higher in patients with isolated AB than in those with non-baumannii Acinetobacter spp. (46.7% vs. 8.3%, P < 0.001). After 2010, complete genotype replacement was observed from non-CC92 genotypes to only CC92 genotypes. Carbapenem resistance rates were highest in AB CC92 (94.2%), followed by AB non-CC92 (12.5%) and non-baumannii Acinetobacter spp. (2.1%). During 2014-2017, which included clustered cases of invasive ST395, colistin resistance increased to 62.5% (n = 10/16), showing a mortality rate of 88% during this period. CONCLUSION: Complete genotype replacement of non-CC92 with CC92 genotypes was observed. AB CC92 was extensively drug-resistant, and pandrug resistance was observed depending on the ST, warranting careful monitoring.

Threshold of Quantitative Cytomegalovirus DNA PCR for Preemptive Treatment in Pediatric Hematopoietic Stem Cell Transplant Recipients.

BACKGROUND: Consensus cytomegalovirus (CMV) DNA viral load thresholds for intervention in hematopoietic stem cell transplant (HSCT) recipients have not been established, especially in children. This study aimed at obtaining viral load thresholds of CMV DNA to guide preemptive management in pediatric HSCT recipients. MATERIALS AND METHODS: A total of 465 blood samples from 177 children who received HSCT between 2015 and 2019 were included in a single center in Korea. The samples were analyzed for CMV infection by both antigenemia assay and quantitative DNA polymerase chain reaction. The 2 assay results were compared for the 233 samples which were collected when antiviral treatment has not been initiated. We determined the viral loads corresponding to the antigenemia of 5 pp65-positive cells/2×10 5 white blood cells (WBCs) as the level for initiating preemptive therapy. RESULTS: Sixty percent of the samples were collected within 100 days (39.7% in 0 to 50 d, 60.2% in 0 to 100 d) from the graft infusion. The correlation between CMV DNA viral load and CMV antigenemia level increased significantly after 50 days from the graft infusion ( r =0.71 vs. r =0.93, P <0.0001). The correlation was greater in the antiviral treatment-naive group than the treatment group ( r =0.75 vs. r =0.66, P <0.0001). Under receiver operating characteristic curve analysis of the treatment-naive group, the estimated threshold CMV DNA viral loads corresponding to 5 pp65-positive cells/2×10 5 WBCs was 898 IU/mL. CONCLUSIONS: The CMV DNA levels that corresponded to 5 pp65-positive cells/2×10 5 WBCs was 900 IU/mL in the HSCT group. The proposed viral load thresholds can be used to guide preemptive therapy in pediatric HSCT recipients, especially in the preengraftment period.

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.

Etiology and Clinical Characteristics of Community-Acquired Pneumonia in Korean Children During the Pre-COVID-19 Period, 2015-2020.

BACKGROUND: There have been many epidemiologic studies on community-acquired pneumonia (CAP) among children, most of which had substantial limitations. This study investigated the etiologic distribution and clinical characteristics of CAP in Korean children for 5 years before the coronavirus disease 2019 (COVID-19) pandemic. METHODS: A retrospective analysis of children hospitalized for CAP at 4 referral hospitals during 2015-2020 was performed. Cases in which bronchiolitis was suspected or pulmonary infiltration was not evident on chest radiography (CXR) were excluded. Viruses and atypical bacteria were defined as detected when positive in the polymerase chain reaction test performed for respiratory specimens. Serologic testing result for Mycoplasma pneumoniae was incorporated with strict interpretation. Pyogenic bacteria were included only when cultured in blood, pleural fluid, or bronchoalveolar lavage, but those cultured in endotracheal aspirate or sputum when the case was clinically evident bacterial pneumonia were also included. RESULTS: A total of 2,864 cases of suspected pneumonia were selected by diagnosis code and CXR findings. Medical chart and CXR review excluded nosocomial pneumonia and cases without evident infiltration, resulting in 517 (18.1%) CAP cases among 489 children. Regarding clinical symptoms, high fever was present in 59.4% and dyspnea in 19.9% of cases. Respiratory support was required for 29.2% of patients, including mechanical ventilation for 3.9%. Pathogens were detected in 49.9% of cases, with viruses in 32.3%, atypical bacteria in 17.8%, and pyogenic bacteria in 2.3% of cases. As single pathogens, M. pneumoniae (16.8%) and respiratory syncytial virus (RSV, 13.7%) were the most common. Parenteral ß-lactam and macrolide antibiotics were administered in 81.6% and 50.7% of cases, respectively. A total of 12 (2.3%) cases resulted in poor outcomes, including 3 deaths. CONCLUSION: M. pneumoniae and RSV were the most commonly detected pathogens of pediatric CAP, which was selected by strict clinical and radiologic criteria. It is necessary to carefully decide whether to use parenteral antibiotics based on the epidemiology and clinical features of CAP in children.

Change in Severity and Clinical Manifestation of MIS-C Over SARS-CoV-2 Variant Outbreaks in Korea.

BACKGROUND: There is difference in the incidence of multi-system inflammatory syndrome in children (MIS-C) in patients with different variants of severe acute respiratory syndrome coronavirus 2, however, little is known about the epidemiology in Asian countries. We investigated and compared the epidemiology of the MIS-C during omicron-dominant period with that of previous periods in South Korea. METHODS: We obtained clinical, epidemiological and laboratory data on MIS-C cases from national MIS-C surveillance in South Korea. We defined pre-delta period as January 2020-May 2021; delta period as June 2021-December 2021; and omicron period as January 2022-April 2022. We describe the clinical characteristics and outcomes of MIS-C patients by period. RESULTS: A total of 91 cases were assessed to be MIS-C cases. Number of MIS-C cases have increased from six cases during pre-delta period to 66 cases during omicron period, while the incidence rate (the number of MIS-C cases per 100,000 cases of reported coronavirus disease 2019) has decreased from 38.5 cases per 100,000 (95% confidence interval [CI], 14.1-83.9) during pre-delta period to 1.6 cases per 100,000 (95% CI, 1.2-2.0) during omicron periods. During pre-delta period, 66.7% and 100% had hypotension and gastrointestinal involvement, respectively; while during omicron period, 12.1% and 6.1% had such clinical manifestations. Fifty percent of pre-delta MIS-C patients were taken intensive care unit (ICU) cares, while 10.6% of patients during omicron periods were in ICUs. CONCLUSION: Omicron period were associated with less severe clinical manifestation compared to pre-delta and delta periods. Although incidence rate of MIS-C was lower for the omicron period than pre-delta and delta periods, number of patients reported with MIS-C may pose a substantial clinical burden.

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.

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.

Outbreak of COVID-19 among children and young adults in a cancer centre daycare unit.

Nosocomial transmission of COVID-19 among immunocompromised hosts can have a serious impact on COVID-19 severity, underlying disease progression and SARS-CoV-2 transmission to other patients and healthcare workers within hospitals. We experienced a nosocomial outbreak of COVID-19 in the setting of a daycare unit for paediatric and young adult cancer patients. Between 9 and 18 November 2020, 473 individuals (181 patients, 247 caregivers/siblings and 45 staff members) were exposed to the index case, who was a nursing staff. Among them, three patients and four caregivers were infected. Two 5-year-old cancer patients with COVID-19 were not severely ill, but a 25-year-old cancer patient showed prolonged shedding of SARS-CoV-2 RNA for at least 12 weeks, which probably infected his mother at home approximately 7-8 weeks after the initial diagnosis. Except for this case, no secondary transmission was observed from the confirmed cases in either the hospital or the community. To conclude, in the day care setting of immunocompromised children and young adults, the rate of in-hospital transmission of SARS-CoV-2 was 1.6% when applying the stringent policy of infection prevention and control, including universal mask application and rapid and extensive contact investigation. Severely immunocompromised children/young adults with COVID-19 would have to be carefully managed after the mandatory isolation period while keeping the possibility of prolonged shedding of live virus in mind.

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.

Shift in Clinical Epidemiology of Human Parainfluenza Virus Type 3 and Respiratory Syncytial Virus B Infections in Korean Children Before and During the COVID-19 Pandemic: A Multicenter Retrospective Study.

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. Demographic and clinical data were extracted from the subject's medical records and analyzed for each virus. RESULTS: A total of 652 children with PIV3 were identified including three epidemics: 216 in 2018, 260 in 2019, and 167 in 2021. Among 627 RSV B cases, 169 were identified in 2017/2018, 274 in 2019/2020, and 115 in 2021/2022. The peak circulation of PIV3 and RSV B epidemics were delayed by 6 and 2 months, respectively, in 2021, compared with those in the pre-COVID-19 period. The median age of PIV3 infections increased in 2021 (21.5 months in 2021 vs. 13.0-14.0 in 2018-2019; P < 0.001), whereas that of RSV B infections remained unchanged (3.6-4.0 months). During the COVID-19 pandemic, less frequent hospitalization rates were observed for both PIV3 and RSV B infections, but more children needed respiratory assistance for RSV B infection in 2021/2022 epidemic (32.5%) than before (14.7-19.4%, P = 0.014). CONCLUSION: We observed changes in the epidemiology and clinical presentation of PIV3 and RSV B infections in Korean children during the COVID-19 pandemic.

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.

Surveillance of COVID-19-Associated Multisystem Inflammatory Syndrome in Children, South Korea.

A concerning development during the coronavirus disease pandemic has been multisystem inflammatory syndrome in children. Reports of this condition in East Asia have been limited. In South Korea, 3 cases were reported to the national surveillance system for multisystem inflammatory syndrome in children. All case-patients were hospitalized and survived with no major disease sequelae.

Efficacy of tetracyclines and fluoroquinolones for the treatment of macrolide-refractory Mycoplasma pneumoniae pneumonia in children: a systematic review and meta-analysis.

BACKGROUND: Mycoplasma pneumoniae is a common pathogen that causes community-acquired pneumonia in school-age children. Macrolides are considered a first-line treatment for M. pneumoniae infection in children, but macrolide-refractory M. pneumoniae (MRMP) strains have become more common. In this study, we assessed the efficacy of tetracyclines and fluoroquinolones in MRMP treatment in children through a systematic review and meta-analysis. METHODS: Two reviewers individually searched 10 electronic databases (Medline/Pubmed, Embase, the Cochrane Library, and core Korean, Chinese, and Japanese journals) for papers published from January 1, 1990 to March 8, 2018. The following data for each treatment group were extracted from the selected studies: intervention (tetracyclines and fluoroquinolones/comparator), patient characteristics (age and sex), and outcomes (fever duration, hospital stay length, treatment success rate, and defervescence rates 24, 48, and 72 h after starting treatment). RESULTS: Eight studies involving 537 participants were included. Fever duration and hospital stay length were shorter in the tetracycline group than in the macrolide group (weighted mean difference [WMD] = - 1.45, 95% confidence interval [CI]: - 2.55 to - 0.36, P = 0.009; and WMD = - 3.33, 95% CI: - 4.32 to - 2.35, P < 0.00001, respectively). The therapeutic efficacy was significantly higher in the tetracycline group than in the macrolide group (odds ratio [OR]: 8.80, 95% CI: 3.12-24.82). With regard to defervescence rate, patients in the tetracycline group showed significant improvement compared to those in the macrolide group (defervescence rate after 24 h, OR: 5.34, 95% CI: 1.81-15.75; after 48 h, OR 18.37, 95% CI: 8.87-38.03; and after 72 h, OR: 40.77, 95% CI: 6.15-270.12). There were no differences in fever improvement within 24 h in patients in the fluoroquinolone group compared to those in the macrolide group (OR: 1.11, 95% CI: 0.25-5.00), although the defervescence rate was higher after 48 h in the fluoroquinolone group (OR: 2.78, 95% CI: 1.41-5.51). CONCLUSION: Tetracyclines may shorten fever duration and hospital stay length in patients with MRMP infection. Fluoroquinolones may achieve defervescence within 48 h in patients with MRMP infection. However, these results should be carefully interpreted as only a small number of studies were included, and they were heterogeneous.

Clinical aspects for differential diagnosis of Kawasaki disease shock syndrome: a case control study.

BACKGROUND: Because of the absence of a specific diagnostic test and pathognomonic clinical features, physicians must rely on the presence of specific clinical criteria and laboratory data that support the diagnosis of KD. To help clinicians distinguish KD, KDSS, septic shock, and TSS earlier, we suggest differential diagnosis and treatment guideline. METHODS: Medical records of immunocompetent patients who were admitted to the pediatric department with a diagnosis of KDSS, septic shock or TSS (SS group) were retrospectively reviewed. In addition, KD patients were selected by seasonal matching to each case of KDSS patient by date of admission (± 2 weeks). RESULTS: There were 13 patients with KDSS, 35 patients with SS group, and 91 patients with KD. In comparison between KDSS and septic shock group, KDSS group had significantly higher rate of coronary aneurysm incidence, and higher left ventricle dysfunction rate. In comparison between KDSS and TSS, patients with KDSS had a significantly higher erythrocyte sedimentation rate (ESR) and significantly lower creatinine. Receiver operation characteristic curve revealed that the optimal ESR cut off value for determining the KDSS was 56.0 (sensitivity 75.0%, specificity of 100.0%) and the optimal creatinine cut off value for determining the TSS was 0.695 (sensitivity 76.9%, specificity 84.6%). CONCLUSIONS: Clinical symptoms, laboratory finding, echocardiography, and culture studies can be used to differentiate KD, KDSS, septic shock and TSS.

Antimicrobial Resistance and Molecular Analysis of Staphylococcus aureus in Staphylococcal Scalded Skin Syndrome among Children in Korea.

BACKGROUND: Staphylococcal scalded skin syndrome (SSSS) is a skin disease characterized by blistering and desquamation caused by exfoliative toxins (ETs) of Staphylococcus aureus (S. aureus). Although many countries show predominance of methicillin-susceptible S. aureus (MSSA), cases of methicillin-resistant S. aureus (MRSA) have been reported. METHODS: Twenty-six children aged <15 years diagnosed with SSSS from January 2010 to December 2017 from three hospitals were included. S. aureus isolates from cases were analyzed for multilocus sequence types and ETs. Medical records were reviewed for clinical characteristics, treatment, and antimicrobial susceptibility patterns of S. aureus. RESULTS: Among the 26 cases, mean age was 2.3 years. According to skin manifestations patients were classified as generalized (n = 10, 38.5%), intermediate (n = 11, 42.3%), and abortive (n = 5, 19.2%). Among all cases, 96.2% (25/26) were due to MRSA and the macrolide-resistance rate was 92.3% (24/26). ST89 (n = 21, 80.8%) was the most prevalent clone, followed by single clones of ST1, ST5, ST72, ST121, and ST1507. The eta gene was detected in one (3.8%) isolate which was MSSA. The etb gene was detected in 14 (53.8%) isolates, all of which were ST89. Nafcillin or first-generation cephalosporin was most commonly prescribed (n=20, 76.9%). Vancomycin was administered in four patients (15.4%) and clindamycin in nine patients (34.6%). Among MRSA cases, there was no difference in duration of treatment when comparing the use of antimicrobials to which the causative bacteria were susceptible or non-susceptible (9.75 vs. 8.07 days, P > 0.05). CONCLUSION: S. aureus isolated from children with SSSS in Korea demonstrated a high prevalence of methicillin-resistant ST89 clones that harbored the etb gene. The predominance of MRSA suggests that antibiotics to which MRSA are susceptible may be considered for empirical antibiotic treatment in children with SSSS in Korea. Further studies on the role and effectiveness of systemic antibiotics in SSSS are warranted.

Waning Effectiveness of One-dose Universal Varicella Vaccination in Korea, 2011-2018: a Propensity Score Matched National Population Cohort.

BACKGROUND: Despite high coverage (~98%) of universal varicella vaccination (UVV) in the Republic of Korea since 2005, reduction in the incidence rate of varicella is not obvious. The study aimed to evaluate the vaccine effectiveness (VE) of one-dose UVV by timeline and severity of the disease. METHODS: All children born in Korea in 2011 were included for this retrospective cohort study that analyzed insurance claims data from 2011-2018 and the varicella vaccination records in the immunization registry. Adjusted hazard ratios by Cox proportional hazard models were used to estimate the VE through propensity score matching by the month of birth, sex, healthcare utilization rate, and region. RESULTS: Of the total 421,070 newborns in the 2011 birth cohort, 13,360 were matched for age, sex, healthcare utilization rate, and region by the propensity score matching method. A total of 55,940 (13.29%) children were diagnosed with varicella, with the incidence rate 24.2 per 1000 person-year; 13.4% of vaccinated children and 10.4% of unvaccinated children. The VE of one-dose UVV against any varicella was 86.1% (95% confidence interval [CI], 81.4-89.5) during the first year after vaccination and 49.9% (95% CI, 43.3-55.7) during the 6-year follow-up period since vaccination, resulting in a 7.2% annual decrease of VE. The overall VE for severe varicella was 66.3%. The VE of two-dose compared to one-dose was 73.4% (95% CI, 72.2-74.6). CONCLUSION: We found lower long-term VE in one-dose vaccination and waning of effectiveness over time. Longer follow ups of the vaccinated children as well as appropriately designed studies are needed to establish the optimal strategy in preventing varicella in Korea.

Limited Benefit of Facility Isolation and the Rationale for Home Care in Children with Mild COVID-19.

Considering the mild degree of coronavirus disease 2019 (COVID-19) in children and the enormous stress caused by isolation in unfamiliar places, policies requiring mandatory isolation at medical facilities should be reevaluated especially given the impact of the pandemic on the availability of hospital beds. In this study, we assessed the usefulness of facility isolation and the transmissibility of severe acute respiratory syndrome coronavirus 2 by infected children to uninfected caregivers in isolation units at a hospital and a residential treatment center in Seoul during August-November 2020. Fifty-three children were included and median age was 4 years (range, 0-18). All were mildly ill or asymptomatic and isolated for a median duration of 12 days. Thirty percent stayed home longer than 2 days before entering isolation units from symptom onset. Among 15 uninfected caregivers, none became infected when they used facemasks and practiced hand hygiene. The results suggest children with mild COVID-19 may be cared safely at home by a caregiver in conditions with adherence to the preventive measures of wearing facemasks and practicing hand hygiene.

Epidemiology and Clinical Features of Myocarditis/Pericarditis before the Introduction of mRNA COVID-19 Vaccine in Korean Children: a Multicenter Study.

BACKGROUND: Korean health authority plans to vaccinate adolescents against coronavirus disease 2019 (COVID-19) starting high school seniors during the summer vacation of 2021. However, the myocarditis/pericarditis following COVID-19 vaccine has been reported recently in adolescents and young adults. This study was performed to answer the urgent questions about the basic epidemiology and clinical course of myocarditis/pericarditis in hospitalized patients prior to the introduction of COVID-19 vaccines in pediatric population. METHODS: A retrospective medical record analysis including frequency, clinical characteristics, etiology and outcome of myocarditis/pericarditis was conducted in 17 years and younger patients who were hospitalized in two referral hospitals in Korea between 2010 and 2019. RESULTS: Total 142 patients with myocarditis (n = 119) and/or pericarditis (n = 23) were identified. Median age was 5.4 years (interquartile range, 0.6-12.9 years; range, 11 days-17.8 years), and male was 61%. In adolescents aged 12-17 years, the male to female ratio was 3.2. Myocarditis/pericarditis occurred 0.70 per 1,000 in-patients during the study period: 0.96 (< 1 year), 0.50 (1-5 years), 0.67 (6-11 years) and 1.22 (12-17 years) per 1,000 in-patients, respectively. There was an increasing tendency for the annual frequency from 0.34 in 2010 to 1.25 per 1,000 in-patients in 2019 (P = 0.021). Among the 56 (40%) proven pathogens at admission, Mycoplasma pneumoniae (n = 11, 8%) and enterovirus (n = 10, 7%) were most common. Of the 142 patients, 99 (70%) required pediatric intensive care unit care and 10 (7%) received heart transplantation. In addition, 61 patients (61/131, 47%) without heart medication at admission needed heart medication when they were discharged. Eleven (7.7%) patients died, of which five patients were previously healthy. The median age of deceased patients was lower than the survival group (0.8 vs. 6.3 years, P = 0.014). CONCLUSION: The frequency of myocarditis/pericarditis was highest among male adolescent in-patients; however, the outcome was favorable in this group without any mortality.