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Croup is an acute upper respiratory disease primarily caused by the parainfluenza virus. Owing to inflammation and edema of the upper airways, children present with barky cough and stridor, and some may experience respiratory distress. We investigated children aged5 years with coronavirus disease 2019 (COVID-19) admitted to two hospitals in Seoul, South Korea, and observed a spike in croup cases during the omicron surge. Among the 569 children admitted from March 1, 2021 to February 25, 2022, 21 children (3.7%) had croup, and the proportion of croup cases was significantly higher during the omicron wave than that during the delta wave (12.4% vs. 1.2%

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., Graphical Abstract

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., Graphical Abstract

The large outbreak of coronavirus disease 2019 (COVID-19) that started in Wuhan, China has now spread to many countries worldwide. Current epidemiologic knowledge suggests that relatively few cases are seen among children, which limits opportunities to address pediatric specific issues on infection control and the children's contribution to viral spread in the community. Here, we report the first pediatric case of COVID-19 in Korea. The 10-year-old girl was a close contact of her uncle and her mother who were confirmed to have COVID-19. In this report, we present mild clinical course of her pneumonia that did not require antiviral treatment and serial viral test results from multiple specimens. Lastly, we raise concerns on the optimal strategy of self-quarantine and patient care in a negative isolation room for children., Graphical Abstract

Background Mycobacterium bovis Bacille Calmette-Guérin (BCG) osteitis, a rare complication of BCG vaccination, has not been well investigated in Korea. This study aimed to evaluate the clinical characteristics of BCG osteitis during the recent 10 years in Korea. Methods Children diagnosed with BCG osteitis at the Seoul National University Children's Hospital from January 2007 to March 2018 were included. M. bovis BCG was confirmed by multiplex polymerase chain reaction (PCR) in the affected bone. BCG immunization status and clinical information were reviewed retrospectively. Results Twenty-one patients were diagnosed with BCG osteitis and their median symptom onset from BCG vaccination was 13.8 months (range, 6.0–32.5). Sixteen children (76.2%) received Tokyo-172 vaccine by percutaneous multiple puncture method, while four (19.0%) and one (4.8%) received intradermal Tokyo-172 and Danish strain, respectively. Common presenting symptoms were swelling (76.2%), limited movement of the affected site (63.2%), and pain (61.9%) while fever was only accompanied in 19.0%. Femur (33.3%) and the tarsal bones (23.8%) were the most frequently involved sites; and demarcated osteolytic lesions (63.1%) and cortical breakages (42.1%) were observed on plain radiographs. Surgical drainage was performed in 90.5%, and 33.3% of them required repeated surgical interventions due to persistent symptoms. Antituberculosis medications were administered for a median duration of 12 months (range, 12–31). Most patients recovered without evident sequelae. Conclusion Highly suspecting BCG osteitis based on clinical manifestations is important for prompt management. A comprehensive national surveillance system is needed to understand the exact incidence of serious adverse reactions following BCG vaccination and establish safe vaccination policy in Korea., Graphical Abstract