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BackgroundEvidence regarding the effectiveness of contact tracing of COVID-19 and the related social distancing is limited and inconclusive. ObjectiveThis study aims to investigate the epidemiological characteristics of SARS-CoV-2 transmission in South Korea and evaluate whether a social distancing campaign is effective in mitigating the spread of COVID-19. MethodsWe used contract tracing data to investigate the epidemic characteristics of SARS-CoV-2 transmission in South Korea and evaluate whether a social distancing campaign was effective in mitigating the spread of COVID-19. We calculated the mortality rate for COVID-19 by infection type (cluster vs noncluster) and tested whether new confirmed COVID-19 trends changed after a social distancing campaign. ResultsThere were 2537 patients with confirmed COVID-19 who completed the epidemiologic survey: 1305 (51.4%) cluster cases and 1232 (48.6%) noncluster cases. The mortality rate was significantly higher in cluster cases linked to medical facilities (11/143, 7.70% vs 5/1232, 0.41%; adjusted percentage difference 7.99%; 95% CI 5.83 to 10.14) and long-term care facilities (19/221, 8.60% vs 5/1232, 0.41%; adjusted percentage difference 7.56%; 95% CI 5.66 to 9.47) than in noncluster cases. The change in trends of newly confirmed COVID-19 cases before and after the social distancing campaign was significantly negative in the entire cohort (adjusted trend difference –2.28; 95% CI –3.88 to –0.68) and the cluster infection group (adjusted trend difference –0.96; 95% CI –1.83 to –0.09). ConclusionsIn a nationwide contact tracing study in South Korea, COVID-19 linked to medical and long-term care facilities significantly increased the risk of mortality compared to noncluster COVID-19. A social distancing campaign decreased the spread of COVID-19 in South Korea and differentially affected cluster infections of SARS-CoV-2.

Introduction: Studies investigating the potential impact of systemic steroid exposure during early infancy on neurological development in full-term infants with normal birth weight are lacking. Methods: This population-based administrative cohort study used data of national health insurance and a health-screening program for infants and children and included full-term infants who were born in Korea between 2008 and 2012 with normal birth weight and did not have any specific perinatal or neurodevelopmental diseases. The prescription of systemic steroids within the first 3 months of age was mainly considered. The neurological development of children was assessed using the Korean Development Screening Test (K-DST) at 6 years of age. To balance the baseline characteristics of the control and exposed groups, stabilized inverse probability of treatment weighting with trimming was performed in the main cohort. Ordinal logistic regression was used to assess the association between systemic steroid exposure and unfavorable results in the K-DST. Results: The control and exposure groups had 246,168 and 5,083 children, respectively. The K-DST suggested unfavorable results in 8.1% and 8.6% children in the control and exposure groups, respectively (weighted odds ratio, 95% confidence interval, 1.03, 0.93–1.14). When each domain of the K-DST was considered separately, the risk of unfavorable results in the exposed group was not significantly different from that in the control group. Conclusions: No significant association was observed between exposure to systemic steroids during early infancy and neurodevelopmental impairment at 6 years of age. [ABSTRACT FROM AUTHOR]

Background: Individuals with atopic dermatitis often develop other conditions. Objective: This study aimed to determine how atopic dermatitis comorbidities develop in children over time. Methods: This population‐based administrative cohort study used national health insurance data. We traced individuals born in Korea between 2002 and 2003 to 2018. The date of initial atopic dermatitis diagnosis was set as the index date. Fifty‐three childhood comorbidities of atopic dermatitis were identified as outcomes of interest by performing a comprehensive literature search and comparing the prevalence of diagnostic codes in children with and without atopic dermatitis. Four control children per individual in the atopic dermatitis group were randomly matched based on sex and index date. The association between atopic dermatitis and the development of each specified disease was assessed using proportional hazard assumption, followed by mapping of the temporal sequences of interconnected comorbidities. Results: The atopic dermatitis and control groups contained 67,632 and 270,528 individuals, respectively. The median age at the index date was 10 months, whereas the median follow‐up period was 15 years. Twenty diseases that were associated with a higher risk of atopic dermatitis were identified and a chain of interconnected conditions created. The progression began in childhood with febrile seizures, constipation, and asthma, and was later associated with the emergence of food allergy, allergic rhinitis, psychiatric disorders, and autoimmune diseases. Conclusion: Our study highlights the temporal nature of atopic dermatitis comorbidities in children, and indicates that an understanding of the comorbidities may inform its clinical management and treatment. [ABSTRACT FROM AUTHOR]

Background: Although atopic dermatitis (AD) in children affects diverse stages of life, no studies have reported on the association between school readiness and AD. Methods: This study used Korean National Health Insurance data and the Health Screening Program for Infants and Children. Among all children born between 2008 and 2012 in Korea, those who were assessed for school readiness through questionnaires in a health screening program performed at 54 and 60 months old were enrolled. AD was defined based on the International Classification of Diseases codes, with two or more prescriptions of topical corticosteroids during the first 54–60 months of life. The primary outcome was the association between school readiness and AD. The questionnaire relating to school readiness comprised six items – cognitive skills, social development, activeness, concentration, emotional development, and language skills. Logistic regression analysis was used to identify the associations between school readiness and AD. Results: This study included 239,673 children without AD and 38,229 children with AD. The average age at which school readiness was assessed was 4.8 years. AD was associated with vulnerability in activeness (adjusted odds ratio: 1.127; 95% confidence interval: 1.071–1.186) and concentrations (1.170; 1.093–1.254). The impact of AD on concentrations showed consistent results regardless of sex, exposure to systemic corticosteroids and antihistamines, and age at the diagnosis of AD. Conclusions: Children with AD have vulnerability in school readiness in the aspects of activeness and concentration. [ABSTRACT FROM AUTHOR]

Background: The optimal time of starting complementary foods (CFs) in infants remains a subject of debate. This population‐based longitudinal cohort study evaluated the association between early CF introduction and body mass index (BMI) in children aged 5–7 years. Methods: The present study included 917,707 children born in Korea during 2008–2009. Initial timing of CF introduction was obtained by questionnaires administered between 4 and 6 months and 9 and 12 months of age. The cohort consisted of 154,565 eligible individuals who properly completed the screening programme, including structured questionnaires, anthropometric measurements and physical examinations. To balance baseline characteristics, children were subjected to propensity score matching based on 95 covariates, including indicators of baseline health such as perinatal condition, birth weight, economic status, clinical disease and drug exposure. Exposure was defined as introduction to CF at age < 4 months, and outcomes were overweight (BMI z‐score > 85th percentile) and obesity (BMI z‐score > 95th percentile) at ages 5–7 years. Results: Of the 154,565 eligible children in the observed cohort, 10,499 (6.8%) were introduced to CF at age < 4 months and 144,066 (93.2%) at age ≥ 4 months. Propensity score matching yielded 9680 children introduced to CF at age < 4 months and 35,396 at age ≥ 4 months. The risk for being overweight or obese at age 5–7 years was slightly higher among those who started CF at age < 4 months than at age ≥4 months (adjusted relative risk = 1.06; 95% confidence interval = 1.02–1.09). A similar but stronger association was observed for being obese at age 5–7 years (adjusted relative risk = 1.12; 95% confidence interval = 1.05–1.19). Conclusions: Early CF introduction before age 4 months was associated with increased BMI at age 5–7 years. Key points: The optimal time of starting complementary foods (CFs) in infants remains a subject of debate.Early CF introduction before age 4 months was associated with increased body mass index (BMI) at age 5–7 years, which suggest that introducing CFs after 4 months as adherence to current guidelines is desirable regarding children's body mass.Physicians, parents, and caregivers of infants should be aware that early CF introduction is associated with increased childhood BMI. [ABSTRACT FROM AUTHOR]

Background: There is a lack of longitudinal studies of associations between growth from infancy to childhood and asthma development. Objective: The objective of the study was to investigate the effects of weight change during infancy, body mass index (BMI) and the interaction of these factors on the risk of childhood asthma. Methods: We enrolled children born in 2008 and 2009 at full‐term and with normal birth weight. The weight change in infancy was grouped into slow, on‐track and rapid. BMI status in childhood was stratified into low, normal and high groups and used as a time‐varying variable. The outcome was asthma, defined as two or more diagnoses of asthma separated by at least 1 year after 2 years of age. The risk of asthma was assessed using Cox proportional hazard regression, with adjustment for sex, residence area at birth, economic status and feeding types in infancy. Results: Of 917,707 children born in Korea in 2008 and 2009, 271,871 were eligible for analysis. The risk of asthma was greater in groups with low birth weight (aHR 1.06, 95% CI 1.04 to 1.08), rapid body weight change during early infancy (aHR 1.08, 95% CI 1.07 to 1.10) and high BMI during childhood (aHR 1.06, 95% CI 1.04–1.08). The interaction of weight change during early infancy with BMI during childhood was significant for asthma (p <.01). Rapid weight gain in infancy was associated with lower risk of asthma in those with low BMI during childhood; had no association with asthma in those with normal BMI during childhood; and was associated increased asthma risk in those with high BMI during childhood—aHR 1.26 (95% CI 1.19 to 1.33) and aHR 1.33 (95% CI 1.12 to 1.56) compared with on‐track and slow infant weight gain, respectively. Conclusion: Low birth weight, high BMI during childhood and, in those with high childhood BMI, rapid weight gain during early infancy are associated with increased risk of childhood asthma. [ABSTRACT FROM AUTHOR]