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Background The prevalence of tuberculosis (TB) in Korean children has decreased due to universal BCG vaccination and the national TB elimination project. However, exposure to TB in children has been consistently reported. There have been few reports of TB exposure in the pediatric hematology-oncology ward. Methods A mother of a pediatric cancer patient was diagnosed with active TB with a cavity. Contact investigation was performed on patients, their parents, and healthcare workers who were exposed to the index case. The criteria for close contact were exposure in the same space with the index patient for more than 8 hours continuously or a total of 40 hours in case of multiple exposures. The initial assessment was performed as soon as the index case was identified. The second evaluation was conducted 8–10 weeks after the initial exposure. Both tuberculin skin test (TST), TB Specific Interferon-Gamma (T-SPOT) tests, and chest radiography were used in immunocompromised pediatric patients. For immunocompetent adults, the QuantiFERON-TB Gold (QFT-G) test and chest radiography were performed. Results Total 23 patients and 29 parents were exposed. The median exposure duration of patients was 3 days (1–8 days). The initial evaluation did not detect TB infection in pediatric patients. However, at the second evaluation, five patients (17.4%) were diagnosed with latent TB infection (LTBI, three with positive TST and two with positive T-SPOT), and two patients (8.7 %) were diagnosed with active TB infection (lymphadenitis and pulmonary TB). Among the 29 parents, 11 individuals (37.9%) were diagnosed with LTBI at the initial evaluation, which was considered as preexisting LTBI before this exposure. No additional case of TB infection was identified in the second evaluation. Among exposed 24 healthcare workers, two (9.1%) were eventually confirmed as newly diagnosed LTBI. Conclusion TB exposure in pediatric hematology-oncology ward and outpatient chemotherapy clinic caused active TB or LTBI cases with an attack rate of 26% in children. The high LTBI rate, up to 38% among parents even before this exposure, needs further intervention such as routine LTBI evaluation and treatment for families of pediatric cancer patients to prevent a similar event. Disclosures Joon-sik Choi, MD, MS, Ministry of Trade, industry and Energy, Republic of Korea: Grant/Research Support Yae-Jean Kim, MD, PhD, Janssen: Grant/Research Support|Korean Society of Pediatric Infectious Diseases: Grant/Research Support|Ministry of Trade, Industry and Energy: Grant/Research Support|MSD: Grant/Research Support.

Background For the 2018–2019 season, the national influenza immunization program expanded to cover children aged from 6 months to 12 years in Korea. This study aimed to analyze vaccine effectiveness (VE) against influenza in children visiting the pediatric emergency room at a tertiary hospital during the 2018-2019 season. Methods Patients tested for influenza antigens from October 1st 2018 to May 31st 2019 at the pediatric emergency room of Samsung Medical Center were included. Patients' influenza antigen test results, influenza vaccination history, and underlying medical conditions were reviewed retrospectively. VE was estimated from the test-negative design study. Results Among the 2,901 visits with influenza test results 1,692 visits of 1,417 patients were included for analysis. Among these 1,417 patients, 285 (20.1%) were positive (influenza A, n = 211, 74.0%; influenza B, n = 74, 26.0%). The VE in all patients was 36.4% (95% confidence interval [CI], 13.9 to 53.1). The VE for influenza A was 37.6% (95% CI, 12.6 to 55.5) and VE for influenza B was 24.0% (−38.5 to 58.3). The VE in the age group 6 months to 12 years was significant with a value of 35.6% (95% CI, 10.5 to 53.7); it was not statistically significant in the age group 13 to 18 years. In a multivariate logistic regression model, patients who received an influenza vaccination were less likely to get influenza infection (OR, 0.6; 95% CI, 0.4 to 0.8; P = 0.001), with significant confounding factors such as age group 13 to 18 years (OR, 0.5; 95% CI, 0.3 to 0.8; P = 0.003) and underlying hematology-oncology disease (OR, 0.3; 95% CI, 0.1 to 0.6; P = 0.002). Conclusion We report moderate effectiveness of influenza vaccination in previously healthy children aged from 6 months to 12 years in the 2018-2019 season., Graphical Abstract

Background Data on severe acute respiratory syndrome coronavirus-2 transmission from a pediatric index patient to others at the school setting are limited. Epidemiological data on pediatric coronavirus disease 2019 (COVID-19) cases after school opening are warranted. Methods We analyzed data of the pediatric patients with COVID-19 collected from the press release of the Korea Centers for Disease Control and Prevention. Information on the school opening delay and re-opening policies were achieved from the press release of the Korean Ministry of Education. Results The school openings were delayed three times in March 2020. Online classes started from April 9, and off-line (in-person) classes started from May 20 to June 8 at four steps in different grades of students. There was no sudden increase in pediatric cases after the school opening, and the proportion of pediatric cases among total confirmed cases in the nation around 7.0%. As of July 31, 44 children from 38 schools and kindergartens were diagnosed with COVID-19 after off-line classes started. More than 13,000 students and staffs were tested; only one additional student was found to be infected in the same classroom. The proportions of pediatric patients without information on infection sources were higher in older age groups than in younger age groups (17.4% vs. 52.4%, P = 0.014). In the younger age group, 78.3% of children were infected by family members, while only 23.8% of adolescents in the older age group were infected by family members (P < 0.001). Conclusion Korea had a successful transition from school closure to online and off-line school opening, which did not cause significant school-related outbreak among the pediatric population., Graphical Abstract

Rationale: The clinical manifestations of VACTERL association include vertebral anomalies, anal atresia, congenital heart diseases, tracheoesophageal fistula, renal dysplasia, and limb abnormalities. The association of intrahepatic anomalies and VACTERL syndrome is a rare coincidence. VACTER syndrome and intrahepatic bile drainage anomalies might be genetically related. Patient concerns: A 12-year-old girl presented with episodic colicky abdominal pain, nausea, and vomiting for several years. The individual episodes resolved spontaneously within a few days. She had a history of VACTERL syndrome, including a butterfly shape of the L3 vertebra, anal atresia, and an atrial septal defect. Diagnoses: On laboratory findings, abnormal liver function tests included elevated total bilirubin, alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyltransferase. There was no significant abnormal finding in hepatobiliary system sonography except mild gallbladder wall thickening. We performed magnetic resonance cholangiopancreatography and demonstrated an abnormal intrahepatic bile duct confluence, which showed 3 bile ducts draining directly into the neck of the gallbladder. Intervention: Her symptoms related to bile reflux during gallbladder contraction. Cholecystectomy with choledochojejunostomy was undertaken because segments of the bile drainage were intertwined. Outcomes: After surgery, her symptoms decreased, but abdominal discomfort remained due to uncorrected left intrahepatic anomalies. Lessons: Although hepatobiliary anomalies are not included in VACTERL association diagnostic criteria, detailed hepatobiliary work up is needed when gastrointestinal symptoms are present in VACTERL association patients.

Atopic dermatitis (AD) is a chronic inflammatory skin disease in children. Patients with AD experience a high rate of colonization of the skin surface by Staphylococcus aureus. Because of a skin barrier defect, there is a potential risk of staphylococcal invasive infection in patients with AD. Here, we present 2 cases of breast abscess caused by S. aureus in 2 adolescent girls with severe AD. Methicillin-sensitive S. aureus was identified from the breast abscess material. They were treated with appropriate antibiotics, however surgical drainage of the abscess was needed in case 1. Identical strains were found from the breast abscess material as well as the lesional and the nonlesional skin of the patients through matrixassisted laser desorption/ionization time-of-flight analysis. We characterized the differential abundance of Firmicutes phylum in patients' skin in microbiota analysis. In particular, S. aureus, a member of Firmicutes, differed significantly between the lesional and the normal-appearing skin. Our cases demonstrate the potential severity of bacterial deep tissue infection in AD and the dysbiosis of skin microbiota may be involved in inflammation in AD.

Background Fungal infection is a serious health threat in high-risk pediatric population. Data on pediatric epidemiology of candidemia in Korea are limited. Methods A retrospective chart review was performed in patients aged 0–18 years who were diagnosed with candidemia from 2009 to 2018 in a tertiary teaching hospital. Patients were divided into two groups; the neonatal group was comprised of babies with postnatal age 28 days or younger and any patients hospitalized in neonatal intensive care unit and rest of the patients were grouped into pediatric group. Only the first candidemia episode for each patient was included. In addition, the number of patients with candidemia and candidiasis and health cost was estimated among patients 19 years or younger who requested reimbursement to Health Insurance Review and Assessment Service (HIRA) Korea during the 9 year period from 2010 to 2018. Results Total 81 patients with candidemia were identified; 42 in the neonatal group and 39 in pediatric group. In neonatal group, prematurity was 95.2%, while hematology-oncology diseases were the most common underlying conditions in pediatric group. Among cultivated candida spp., C. parapsilosis was the most common pathogen (34.6%) followed by C. albicans (32.1%) and C. glabrata and C. tropicalis (11.1%, respectively). In neonatal group, C. parapsilosis (n = 17, 40.5%), C. albicans (n = 16, 38.1%), C. glabrata (n = 5, 11.9%) and unidentified species non-albicans candida (n = 4) were isolated. In pediatric group, C. parapsilosis (n = 11, 28.2%), C. albicans (n = 10, 25.6%), C. tropicalis (n = 9, 23.1%), C. glabrata (n = 4, 10.3%), C. krusei (n = 2), C. orthopsilosis (n = 1), C. lusitaniae (n = 1), C. kefyr (n = 1) were isolated. From HIRA data analysis, 47 patients were found to have candidemia and health cost was estimated as 1.27 million dollars and 66,286 patients were found to have candidiasis and health cost was 2.14 million dollars. Conclusion Discrepancies in numbers for candidemia between national reimbursement data and our retrospective data implies a significant underestimation of candidemia. Increased awareness for fungal infection documentation is needed to better estimate the true burden of invasive candida infection in the pediatric population. Disclosures All authors: No reported disclosures.

Purpose: Lower respiratory tract infection (LRTI) is one of the most common causes of hospitalization in the pediatric population. In this study, we investigated the clinical characteristics of LRTI, particularly in low birth weight children. Methods: We reviewed medical records of children at ages 0-6 years with LRTI in Korea University Anam Hospital between January and December of 2014. Clinical data including age, sex, birth history, viral pathogens, blood test results, and clinical courses were collected. Results: In the 828 eligible cases, 617 (74.5%) were pneumonia and followed by bronchiolitis 180 (21.7%) and bronchitis 31 (3.7%). The median age of the subjects was 17 months (interquartile range [IQR], 7-28 months), the median gestational age was 39.0 weeks (IQR, 38.0-40.0 weeks) and the median birth weight was 3,200 g (IQR, 2,900-3,480 g). Sixty-four children (7.7%) were low birth weight (

Mixed Candida/bacterial bloodstream infections (BSIs) have been reported to occur in more than 23% of all episodes of candidaemia. However, the clinical implications of mixed Candida/bacterial BSIs are not well known. We performed a retrospective case-control study of all consecutive patients with candidaemia over a 5-year period to determine the risk factors for and clinical outcomes of mixed Candida/bacterial BSIs (cases) compared with monomicrobial candidaemia (controls). Thirty-seven (29%) out of 126 patients with candidaemia met the criteria for cases. Coagulase-negative staphylococci were the predominant bacteria (23%) in cases. In multivariate analysis, duration of previous hospital stay >7 weeks (odds ratio (OR), 2.86; 95% confidence interval (CI), 1.09–7.53), prior antibiotic therapy ≥7 days (OR, 0.33; 95% CI, 0.14–0.82) and septic shock at the time of candidaemia (OR, 2.60; 95% CI, 1.14–5.93) were significantly associated with cases. Documented clearance of candidaemia within 3 days after initiation of antifungal therapy was less frequent in cases (63% vs. 84%; p = 0.035). The difference in the rate of treatment failure at 2 weeks was not significant between cases (68%) and controls (62%; p = 0.55). The crude mortality at 6 weeks and survival through 100 days did not differ between the two patient groups (p = 0.56 and p = 0.80, respectively). Mixed Candida/bacterial BSIs showed a lower clearance rate of candidaemia during the early period of antifungal therapy, although the treatment response and survival rate were similar regardless of concurrent bacteraemia. Further studies on the clinical relevance of species-specific Candida-bacterial interactions are needed.