Incidence and risk factors of COVID-19 in a tertiary hospital and the effectiveness of booster vaccination among health care workers: A retrospective cohort study, January 2020 to June 2022

BACKGROUND

Health care workers (HCWs) face a higher risk of infection and may transmit pathogens to patients during a pandemic. This study aims to evaluate infection-control measures by analyzing the incidence and risk factors of COVID-19 and estimating vaccine effectiveness (VE) at a tertiary hospital in Seoul, Republic of Korea.

METHODS

This study included 2,516 HCWs from January 1, 2020, to June 30, 2022. Data were analyzed to determine the incidence density and cumulative incidence; the results were compared by the age- and gender-specific standardized incidence ratios (SIR). VE was estimated with multivariate Cox proportional-hazard models as 1-adjusted hazard ratio × 100%.

RESULTS

SIR indicated a lower COVID-19 risk in the hospital population than in the general Korean population (SIR, 0.81; 95% confidence interval [CI]: 0.76-0.87). Multivariate Cox analysis indicated that, compared to doctors, nonmedical service supporters and other HCWs (excluding doctors and nurses) were high-risk groups (adjusted hazard ratio [95% CI], 1.72 [1.04-2.83] and 1.76 [1.20-2.58], respectively). Compared to the outpatient unit, the emergency department was a high-risk department (1.70 [1.16-2.50]). The VE of the booster dose was 55.47%, compared to no or incomplete vaccination (95% CI: 22.63-74.37).

CONCLUSIONS

Besides encouraging HCWs vaccination, effective infection-control measures should target high-risk groups and departments.

COVID-19 vaccine safety: Background incidence rates of anaphylaxis, myocarditis, pericarditis, Guillain-Barré Syndrome, and mortality in South Korea using a nationwide population-based cohort study

BACKGROUND

To properly assess an association between vaccines and specific adverse events requires a comparison between the observed and background rates; however, studies in South Korea are currently limited. Therefore, in this study, we estimated the background incidence of anaphylaxis, myocarditis, pericarditis, Guillain-Barré syndrome (GBS), and mortality in South Korea.

METHODS

A retrospective cohort study was conducted using the National Sample Cohort (NSC) data. Using NSC, the background incidence rate was estimated by dividing the number of episodes during 2009-2019 by the total population by year and then multiplying by 100,000. Using Statistics Korea data, the background mortality rate was estimated by dividing the number of deaths, during 2009-2019 by the standard population for that year and then multiplying by 100,000. Using background mortality rates, we predicted mortality rates for 2021 using autoregressive integrated moving average models. Further, the expected mortality rates were compared with observed mortality rates.

RESULTS

The age-adjusted incidence rate (AIR) of anaphylaxis increased from 4.28 to 22.90 cases per 100,000 population (p = 0.003); myocarditis showed no significant increase, changing from 0.56 to 1.26 cases per 100,000 population (p = 0.276); pericarditis increased from 0.94 to 1.88 cases per 100,000 population (p = 0.005); and GBS increased from 0.78 to 1.21 cases per 100,000 population (p = 0.013). The age-adjusted mortality rate decreased from 645.24 to 475.70 deaths per 100,000 population (p <0.001). The 2021 observed/expected mortality rates for overall (ratio: 1.08, 95% confidence interval [CI]: 1.07-1.08), men (ratio: 1.07, 95% CI: 1.07-1.08), and women (ratio: 1.08, 95% CI: 1.07-1.09), were all significantly higher. When stratified by age group, those aged ≥80 (ratio: 1.16, 95% CI: 1.15-1.17), 60-69 (ratio: 1.11, 95% CI: 1.10-1.13), and 20-29 years old (ratio: 1.07, 95% CI: 1.02-1.13) were also significantly higher.

CONCLUSION

Through the estimation of background rates related to anaphylaxis, myocarditis, pericarditis, GBS, and mortality, we established a reference point for evaluating the potential excess occurrence of adverse events following COVID-19 vaccination. This reference point serves as substantive evidence supporting the safety profile of COVID-19 vaccines.

Gender Inequalities in Mental Health During the COVID-19 Pandemic: A Population-based Study in Korea

OBJECTIVES

This study explored the effect of the coronavirus disease 2019 (COVID-19) pandemic on psychosocial stress in prime working-age individuals in Korea, focusing on gender inequalities. We hypothesized that the impact of COVID-19 on mental health would differ by age and gender, with younger women potentially demonstrating heightened vulnerability relative to men.

METHODS

The study involved data from the Korea Community Health Survey and included 319 592 adults aged 30 years to 49 years. We employed log-binomial regression analysis, controlling for variables including age, education, employment status, marital status, and the presence of children. The study period included 3 phases: the period prior to the COVID-19 outbreak (pre-COVID-19), the early pandemic, and the period following the introduction of vaccinations (post-vaccination).

RESULTS

The findings indicated that women were at a heightened risk of psychosocial stress during the early pandemic (relative risk [RR], 1.01; 95% confidence interval [CI], 0.98 to 1.05) and post-vaccination period (RR, 1.07; 95% CI, 1.04 to 1.10) compared to men. This pattern was prominent in urban women aged 30-34 years (pre-COVID-19: RR, 1.06; 95% CI, 1.02 to 1.10; early pandemic: RR, 1.16; 95% CI, 1.08 to 1.25; post-vaccination period, RR, 1.22; 95% CI, 1.14 to 1.31).

CONCLUSIONS

The COVID-19 pandemic has exerted unequal impacts on psychosocial stress among prime working-age individuals in Korea, with women, particularly those in urban areas, experiencing a heightened risk. The findings highlight the importance of addressing gender-specific needs and implementing appropriate interventions to mitigate the psychosocial consequences of the pandemic.

Signal detection of COVID-19 vaccines adverse events using spontaneous reports from South Korea

PURPOSE

Studies on the detection of COVID-19 vaccine signals in South Korea are insufficient. Therefore, to investigate adverse events (AEs) that might be associated with COVID-19 vaccines, signals were detected using spontaneous reports from South Korea. We compared the signals with the vaccine insert lists of the regulators in the four countries.

METHODS

Spontaneous reports from 62 sites were collected by the National Medical Center between January 2013 and May 2022. A descriptive analysis of AEs associated with COVID-19 vaccines (Pfizer, Moderna, AstraZeneca, and Janssen) was performed, and the proportional reporting ratio, reporting odds ratio, and information component were calculated. We performed five analyses, with five cases and one control group.

RESULTS

During the study period, 68 355 cases were reported, of which 12 485 were COVID-19 vaccine AEs. Injection site pain (2198 cases, 17.6%), myalgia (1552 cases, 12.4%), headache (1145 cases, 9.2%), pyrexia (1003 cases, 8.0%), and fatigue (735 cases, 5.9%) were frequently reported. When comparing all COVID-19 vaccines with other viral vaccines, 20 signals were detected, of which cachexia, dyspepsia, abdominal discomfort, and mood swings were not listed on the vaccine inserts in all four countries. Overall, 20, 17, 29, and 9 signals were detected in vaccines developed by Pfizer, Moderna, AstraZeneca, and Janssen, respectively.

CONCLUSIONS

Based on a disproportionate analysis of COVID-19 vaccine AEs using spontaneous reports from South Korea, different signals were detected for each vaccine manufacturer.

Effects of Severe Acute Respiratory Syndrome Coronavirus Vaccination on Reinfection: A Community-Based Retrospective Cohort Study

BACKGROUND

Coronavirus disease 2019 (COVID-19) is a disease that is characterized by frequent reinfection. However, the factors influencing reinfection remain poorly elucidated, particularly regarding the effect of COVID-19 vaccination on preventing reinfection and its effects on symptomatology and the interval until reinfection.

METHODS

This retrospective cohort study examined patients with severe acute respiratory syndrome coronavirus reinfection between January 2020 and February 2022. This study included patients aged >17 years who were reinfected at least 90 days between two infections with severe acute respiratory syndrome coronavirus. The main outcome measure was a reduction in symptoms during reinfection, and reinfection interval.

RESULTS

Overall, 712 patients (average age: 40.52 ± 16.41 years; 312 males) were included. The reduction rate of symptoms at reinfection than that at first infection was significantly higher in the vaccinated group than in the unvaccinated group (p < 0.001). The average reinfection interval was 265.81 days. The interval between the first and second infection was 63.47 days longer in the vaccinated group than in the unvaccinated group. The interval was also 57.23 days, significantly longer in the asymptomatic group than in the symptomatic group (p < 0.001).

CONCLUSIONS

Besides its role in preventing severe acute respiratory syndrome coronavirus infection, vaccination reduces the rate of symptomatic reinfection and increases the reinfection interval; thus, it is necessary to be vaccinated even after a previous infection. The findings may inform the decision to avail COVID-19 vaccination.

Assessment of severity scoring systems for predicting mortality in critically ill patients receiving continuous renal replacement therapy

The incidence of acute kidney injury (AKI) is increasing every year and many patients with AKI admitted to the intensive care unit (ICU) require continuous renal replacement therapy (CRRT). This study compared and analyzed severity scoring systems to assess their suitability in predicting mortality in critically ill patients receiving CRRT. Data from 612 patients receiving CRRT in four ICUs of the Korea University Medical Center between January 2016 and November 2018 were retrospectively collected. The mean age of all patients was 67.6 ± 14.8 years, and the proportion of males was 59.6%. The endpoints were in-hospital mortality and 7-day mortality from the day of CRRT initiation to the date of death. The Program to Improve Care in Acute Renal Disease (PICARD), Demirjian's, Acute Physiology and Chronic Health Evaluation (APACHE) II, Simplified Acute Physiology Score (SAPS) 3, Sequential Organ Failure Assessment (SOFA), Multiple Organ Dysfunction Score (MODS), and Liano's scores were used to predict mortality. The in-hospital and 7-day mortality rates in the study population were 72.7% and 45.1%, respectively. The area under the receiver operator characteristic curve (AUROC) revealed the highest discrimination ability for Demirjian's score (0.770), followed by Liano's score (0.728) and APACHE II (0.710). The AUROC curves for the SAPS 3, MODS, and PICARD were 0.671, 0.665, and 0.658, respectively. The AUROC of Demirjian's score was significantly higher than that of the other scores, except for Liano's score. The Hosmer-Lemeshow test on Demirjian's score showed a poor fit in our analysis; however, it was more acceptable than general severity scores. Kidney-specific severity scoring systems showed better performance in predicting mortality in critically ill patients receiving CRRT than general severity scoring systems.

Health behaviors and the risk of COVID-19 incidence: A Bayesian hierarchical spatial analysis

OBJECTIVES

Effective infection control measures, based on a sound understanding of geographical community-specific health behavioral characteristics, should be implemented from the early stage of disease transmission. However, few studies have explored health behaviors as a possible contributor to COVID-19 infection in the spatial context. We investigated health behaviors as potential factors of COVID-19 incidence in the early phase of transmission in the spatial context.

METHODS

We extracted COVID-19 cumulative case data as of February 25, 2021-one day prior to nationwide COVID-19 vaccination commencement-regarding health behaviors and covariates, including health condition and socio-economic factors, at the municipal level from publicly available datasets. The spatial autocorrelation of incidence was analyzed using Global Moran's I statistics. The associations between health behaviors and COVID-19 incidence were examined using Besag-York-Mollie models to deal with spatial autocorrelation of residuals.

RESULTS

The COVID-19 incidence had positive spatial autocorrelation across South Korea (I = 0.584, p = 0.001). The results suggest that individuals vaccinated against influenza in the preceding year had a negative association with COVID-19 incidence (relative risk=0.913, 95 % Credible Interval=0.838-0.997), even after adjusting for covariates.

CONCLUSIONS

Our ecological study suggests an association between COVID-19 infection and health behaviors, especially influenza vaccination, in the early stage of COVID-19 transmission at the municipal level.

Cardio-cerebrovascular complications in COVID-19 patients: A retrospective cohort study

Background

Recent studies have highlighted the cardio-cerebrovascular manifestations of coronavirus disease 2019 (COVID-19).

Objective

This study aimed to analyze the likelihood of cardiovascular and cerebrovascular manifestations among patients with COVID-19-positive individuals in South Korea.

Methods

A cohort database for COVID-19 from the National Health Insurance Service was used which included patients diagnosed with COVID-19 between January 1 and June 4, 2020. Individuals who tested COVID-19 positive, notwithstanding the severity of the disease, were designated as cases. COVID-19- negative individuals were used as controls for the study. The exclusion criteria included people who had a history of cardiovascular and cerebrovascular diseases between 2015 and 2019. A new diagnosis of cardiovascular and cerebrovascular complications was considered the primary endpoint. The adjusted incidence rate ratio (IRR) of development of complications was estimated using log-link Poisson regression. The model was adjusted at two levels, the first one included age and sex while the second included age, sex, residence area, and level of income. The hazard ratio (HR) was estimated using Cox-proportional hazard regression analysis while adjusting for all demographic variables and covariates.

Results

Significant results were obtained for acute conditions, such as ischemic heart disease and cerebral hemorrhage. The IRR of COVID-19- positive individuals compared with that of controls for the diagnosis of ischemic heart disease was 1.78 (1.57-2.02; 95% confidence interval [CI]) when adjusted for age and sex. HR was calculated as 3.02 (2.19-4.17; 95% CI) after adjusting for the covariates. In case of cerebral hemorrhage, the adjusted IRR was 2.06 (1.25-3.40; 95% CI) and the adjusted HR was 4.08 (0.90-19.19; 95% CI).

Conclusion

The findings of our study suggest that COVID-19 infection can be a significant risk factor for acute cardiovascular complications, such as ischemic heart disease and acute cerebrovascular complications, such as cerebral infarction, after properly adjusting for covariates.

Association between Climate Factors and Dengue Fever in Asuncion, Paraguay: A Generalized Additive Model

Dengue fever has been endemic in Paraguay since 2009 and is a major cause of public-health-management-related burdens. However, Paraguay still lacks information on the association between climate factors and dengue fever. We aimed to investigate the association between climatic factors and dengue fever in Asuncion. Cumulative dengue cases from January 2014 to December 2020 were extracted weekly, and new cases and incidence rates of dengue fever were calculated. Climate factor data were aggregated weekly, associations between dengue cases and climate factors were analyzed, and variables were selected to construct our model. A generalized additive model was used, and the best model was selected based on Akaike information criteria. Piecewise regression analyses were performed for non-linear climate factors. Wind and relative humidity were negatively associated with dengue cases, and minimum temperature was positively associated with dengue cases when the temperature was less than 21.3 °C and negatively associated with dengue when greater than 21.3 °C. Additional studies on dengue fever in Asuncion and other cities are needed to better understand dengue fever.

Risk Prediction of Three Different Subtypes of Highly Pathogenic Avian Influenza Outbreaks in Poultry Farms: Based on Spatial Characteristics of Infected Premises in South Korea

From 2003 to 2017, highly pathogenic avian influenza (HPAI) epidemics, particularly H5N1, H5N8, and H5N6 infections in poultry farms, increased in South Korea. More recently, these subtypes of HPAI virus resurged and spread nationwide, heavily impacting the entire poultry production and supply system. Most outbreaks in poultry holdings were concentrated in the southwestern part of the country, accounting for 58.3% of the total occurrences. This geographically persistent occurrence demanded the investigation of spatial risk factors related to the HPAI outbreak and the prediction of the risk of emerging HPAI outbreaks. Therefore, we investigated 12 spatial variables for the three subtypes of HPAI virus-infected premises [(IPs), 88 H5N1, 339 H5N8, and 335 H5N6 IPs]. Then, two prediction models using statistical and machine learning algorithm approaches were built from a case-control study on HPAI H5N8 epidemic, the most prolonged outbreak, in 339 IPs and 626 non-IPs. Finally, we predicted the risk of HPAI H5N1 and H5N6 occurrence at poultry farms using a Bayesian logistic regression and machine learning algorithm model [extreme gradient boosting (XGBoost) model] built on the case-control study. Several spatial variables showed similar distribution between two subtypes of IPs, although there were distinct heterogeneous distributions of spatial variables among the three IP subtypes. The case-control study indicated that the density of domestic duck farms and the minimum distance to live bird markets were leading risk factors for HPAI outbreaks. The two prediction models showed high predictive performance for H5N1 and H5N6 occurrences [an area under the curve (AUC) of receiver operating characteristic of Bayesian model > 0.82 and XGBoost model > 0.97]. This finding emphasizes that spatial characteristics of the poultry farm play a vital role in the occurrence and forecast of HPAI outbreaks. Therefore, this finding is expected to contributing to developing prevention and control strategies.

Ambient Air Pollution and Kawasaki Disease in Korean Children: A Study of the National Health Insurance Claim Data

Background

Kawasaki disease (KD) is a systemic vasculitis of unknown etiology that primarily affects children under 5 years of age. Some researchers suggested a potential triggering effect of air pollution on KD, but the findings are inconsistent and limited by small sample size. We investigated the association between ambient air pollution and KD among the population of South Korea younger than 5 years using the National Health Insurance claim data between 2007 and 2019.

Methods and Results

We obtained the data regarding particulate matter ≤10 or 2.5 µm in diameter, nitrogen dioxide, sulfur dioxide, carbon monoxide, and ozone from 235 regulatory monitoring stations. Using a time‐stratified case‐crossover design, we performed conditional logistic regression to estimate odds ratios (OR) of KD according to interquartile range increases in each air pollutant concentration on the day of fever onset after adjusting for temperature and relative humidity. We identified 51 486 children treated for KD during the study period. An interquartile range increase (14.67 μg/m³) of particulate matter ≤2.5 µm was positively associated with KD at lag 1 (OR, 1.016; 95% CI, 1.004–1.029). An interquartile range increase (2.79 ppb) of sulfur dioxide concentration was associated with KD at all lag days (OR, 1.018; 95% CI, 1.002–1.034 at lag 0; OR, 1.022; 95% CI, 1.005–1.038 at lag 1; OR, 1.017; 95% CI, 1.001–1.033 at lag 2). Results were qualitatively similar in the second scenario of different fever onset, 2‐pollutant model and sensitivity analyses.

Conclusions

In a KD‐focused national cohort of children, exposure to particulate matter ≤2.5 µm and sulfur dioxide was positively associated with the risk of KD. This finding supports the triggering role of ambient air pollution in the development of KD.

Trends of Internet Search Volumes for Major Depressive Disorder Symptoms During the COVID-19 Pandemic in Korea: An Interrupted Time-Series Analysis

BACKGROUND

The effect of coronavirus disease 2019 (COVID-19) pandemic on public mental health has been increasing. Additionally, the underlying psychological stressors remain unexplored, and few studies have been conducted nationally on the social distancing measures. Therefore, the present study aimed to identify the psychological impacts of the implementation of social distancing measures by analyzing the Internet search trends of major depressive disorder (MDD) symptoms.

METHODS

Using Naver^® Trends' relative search volumes (RSVs), we analyzed the average search volumes and trend changes of 16 terms, adopted from the Diagnostic and Statistical Manual of Mental Disorders-5 criteria for diagnosing MDD. An interrupted time-series analysis was performed using the data from January 1, 2016 to December 31, 2020. Furthermore, changes in RSVs, according to the intensity of the social distancing measures implemented from January 1 to December 31, 2020, were determined using Wilcoxon rank sum tests.

RESULTS

Of the 16 terms, the search trends of 'feeling guilty' (P < 0.001) and 'wanting to die' (P = 0.002) showed a significant increase as of February 29, 2020, when the social distancing measures were officially implemented. Additionally, the average search volumes for 'hopelessness' (P = 0.003), 'sexual desire' (P < 0.001), 'insomnia' (P = 0.002), 'hypersomnia' (P < 0.001), 'restlessness' (P < 0.001), and 'feeling lethargic' (P < 0.001) increased significantly. Moreover, gender analysis showed that the average search volume of 'depressed mood' (P = 0.033) and the trend of 'impaired concentration' (P < 0.001) increased in males only. However, the average search volume of 'feeling lethargic' (P = 0.001) and the trend of 'feeling guilty' (P = 0.001) increased in females only. The average search volumes for 'depressed mood' (P < 0.001), 'impaired concentration' (P = 0.038), and 'indecisiveness' (P < 0.001) were significantly higher during the enforcement of level 2 or higher social distancing measures.

CONCLUSION

Our results reported the negative effect of COVID-19 preventive measures on public mental health in South Korea, especially for MDD symptoms. Moreover, the findings suggested the utility of Naver Trends as a feasible big data source to assess future mental health crises.

Socioeconomic Inequalities in COVID-19 Incidence During Different Epidemic Phases in South Korea

Objective

Area-level socioeconomic status (SES) is associated with coronavirus disease 2019 (COVID-19) incidence. However, the underlying mechanism of the association is context-specific, and the choice of measure is still important. We aimed to evaluate the socioeconomic gradient regarding COVID-19 incidence in Korea based on several area-level SES measures.

Methods

COVID-19 incidence and area-level SES measures across 229 Korean municipalities were derived from various administrative regional data collected between 2015 and 2020. The Bayesian negative binomial model with a spatial autocorrelation term was used to estimate the incidence rate ratio (IRR) and relative index of inequality (RII) of each SES factor, with adjustment for covariates. The magnitude of association was compared between two epidemic phases: a low phase (<100 daily cases, from May 6 to August 14, 2020) and a rebound phase (>100 daily cases, from August 15 to December 31, 2020).

Results

Area-level socioeconomic inequalities in COVID-19 incidence between the most disadvantaged region and the least disadvantaged region were observed for nonemployment rates [RII = 1.40, 95% credible interval (Crl) = 1.01–1.95] and basic livelihood security recipients (RII = 2.66, 95% Crl = 1.12–5.97), but were not observed for other measures in the low phase. However, the magnitude of the inequalities of these SES variables diminished in the rebound phase. A higher area-level mobility showed a higher risk of COVID-19 incidence in both the low (IRR = 1.67, 95% Crl = 1.26–2.17) and rebound phases (IRR = 1.28, 95% Crl = 1.14–1.44). When SES and mobility measures were simultaneously adjusted, the association of SES with COVID-19 incidence remained significant but only in the low phase, indicating they were mutually independent in the low phase.

Conclusion

The level of basic livelihood benefit recipients and nonemployment rate showed social stratification of COVID-19 incidence in Korea. Explanation of area-level inequalities in COVID-19 incidence may not be derived only from mobility differences in Korea but, instead, from the country's own context.

Epidemiologic Characteristics and Case Fatality Rate of Vibrio vulnificus Infection: Analysis of 761 Cases From 2003 to 2016 in Korea

BACKGROUND

Vibrio vulnificus infection is a highly fatal disease resulting from the consumption of raw or undercooked seafood and exposure to seawater containing the organism. It has been a nationally notifiable disease since 2000 in Korea. The aims of this study were to assess the trends in the incidence of V. vulnificus infection and its case fatality rate and to determine the epidemiologic characteristics to effectively prevent infection and lower mortality.

METHODS

We analyzed the incidence trends of V. vulnificus infection by year, month, and region in 913 cases reported to the Korea Centers for Disease Control and Prevention (KCDC, currently Korea Disease Control and Prevention Agency) by the National Infectious Disease Surveillance System from 2001 to 2016. We analyzed the number of patients with V. vulnificus infection who were under the National Health Insurance Service (NHIS) and whose coastal seawater temperature data were provided by the Korea Oceanographic Data Center of the National Institute of Fisheries Science. Epidemiological investigations were followed up and analyzed for 761 patients from 2003 to 2016. A total of 152 patients who were not followed up were excluded from the analysis. The case fatality rate was analyzed for 325 cases reported to the KCDC from 2011 to 2016.

RESULTS

The mean incidence of V. vulnificus infection was 0.12 per 100,000 people, and the highest incidence was reported in September (41.1%) during the study period. The incidence rate per 100,000 people was the highest in Jeonnam (8.23). The number of patients who claimed to the NHIS was the highest in September (105 patients). The average seawater temperature was the highest at 24.1°C in August, and the average seawater temperature from August to October, when many cases occurred, was 22.4°C. The male-to-female ratio was 6:1, and 96.4% of the patients were aged ≥ 40 years. Of the patients, 96.1% had underlying diseases, the most common of which was liver cirrhosis (56.3%). The case fatality rate was 48.9%.

CONCLUSION

The occurrence of V. vulnificus infection showed distinct seasonality, with a large number of cases occurring in the months when the seawater temperature was high; there were also distinct geographical characteristics. The incidence of V. vulnificus infection and mortality rates have not decreased for decades, and it is still an important public health problem with a high fatality rate.

Spatiotemporal clusters of Kawasaki disease in South Korea from 2008 to 2017: A municipal-level ecological study

INTRODUCTION

As the etiology of Kawasaki disease (KD) remains unknown, identifying spatiotemporal clusters with proper stratification of KD could provide further evidence for investigating the triggers of KD. However, spatiotemporal distributions of KD with sex stratification have never been reported. Therefore, we aimed to analyze the spatiotemporal patterns of KD by sex in South Korea.

METHODS

We extracted epidemiologic week (Epiweek)-based KD cases in patients <5 years of age (ICD-10-CM code: M303) from 2008 to 2017 national health insurance service data at the 250 municipal level. To determine whether spatial autocorrelation and persistent municipal-level clusters exist, year- and sex-stratified global Moran's I statistics, Getis-Ord Gi* statistics, and emerging hotspot analysis on KD incidence were conducted.

RESULTS

A total of 72,510 KD cases were reported between 2008 and 2017 (male-to-female ratio = 1.40:1). Incidence has increased since 2008, with the highest incidence in 2016 (396.8 per 100,000 population). KD had seasonality of winter and summer but different by sex. Positive spatial autocorrelation was consistently reported in every stratum, with the 2011-2014 period having the strongest index value (total sex I = 0.286, p < 0.001; male I = 0.242, p < 0.001; female I = 0.213, p < 0.001). Hot spots were consistently detected in the northern parts, and cold spots were in the southern part for 9 years in both sexes. The emerging hot spot analysis showed new, consecutive, and sporadic hot spots on the northwestern and eastern coasts and new and sporadic cold spots in the southwestern part. However, the distribution and proportion of hot or cold spot types differed according to sex.

DISCUSSION

The spatiotemporal features of KD had limits to concluding that only infectious triggers result in KD occurrence. Therefore, our findings support the notion that KD is a syndrome with multiple factors, including infectious, genetic, and environmental factors, that are associated with sex differences.

Dynamics of inter-farm transmission of highly pathogenic avian influenza H5N6 integrating vehicle movements and phylogenetic information

Highly pathogenic avian influenza (HPAI) in poultry holdings commonly spreads through animal trade, and poultry production and health-associated vehicle (PPHaV) movement. To effectively control the spread of disease, it is essential that the contact structure via those movements among farms is thoroughly explored. However, few attempts have been made to scrutinize PPHaV movement compared to poultry trade. Therefore, our study aimed to elucidate the role of PPHaV movement on HPAI transmission. We performed network analysis using PPHaV movement data based on a global positioning system, with phylogenetic information of the isolates during the 2016–2017 HPAI H5N6 epidemic in the Republic of Korea. Moreover, the contribution of PPHaV movement to the spread of HPAI was estimated by Bayesian modeling. The network analysis revealed that there was the relationship between phylogenetic clusters and the contact network via PPHaV movement. Furthermore, the similarity of farm poultry species and the shared integrators between inter-linked infected premises (IPs) were associated with ties within the same phylogenetic clusters. Additionally, PPHaV movement among phylogenetically clustered IPs was estimated to contribute to approximately 30% of HPAI H5N6 infections in IPs on average. This study provides insight into how HPAI spread via PPHaV movement and scientific basis for control strategies.

352. COVID-19 Not a Risk Factor of Alopecia Areata: Results of a National Cohort Study in South Korea

Background

There have been approximately 158 million coronavirus disease 2019 (COVID-19) pandemic survivors worldwide by June 9, 2021. As a result, concerns about hair loss in COVID-19 patients have emerged among dermatologists. However, most of extant literature have limited implications by relying on cross-sectional studies with restricted study subjects without control group. Therefore, our study aims to investigate the risk of developing alopecia areata (AA) among COVID-19 patients in South Korea using adequate control based on national representative data.

Methods

We used the National Health Insurance Service (NHIS) COVID‐19 cohort database, comprising COVID‐19 patient and control group, all of whom were diagnosed from January 1, 2020 to June 4, 2020. Patients were defined as individuals who were confirmed as COVID‐19 positive, regardless of disease severity. Controls were defined as whom confirmed as COVID‐19 negative. People with a history of AA during the period 2015–2019 were excluded. The primary endpoint was a new diagnosis of AA (ICD-10-CM-Code: L63). Adjusted incidence rate ratio (IRR) of developing AA was estimated using log-link Poisson regression model based on incidence density of case and control group. The model adjusted for (1) age and sex (2) demographic variables (age, sex, place of residence, and income level). Statistical significance was set at p< 0.05.

Results

A total of 226,737 individuals (7,958 [3.5%] cases and 218,779 [96.5%] controls) were included in the final analysis. There were more females than males, both in test positives and negatives at 59.9% and 52.3%, respectively. The largest test positive population was those in age group 20 to 29 years (25.5%),. The test negatives had the largest population in age group 30 to 39 years (17.1%). The ratio of newly diagnosed AA was 18/7,958 (0.2%) in cases and 195/218,779 (0.1%) in controls. IRRs of COVID-19 patients having newly diagnosed AA compared to controls were 0.78 (0.48‒1.27) when age and sex were adjusted for, and 0.60 (0.35‒1.03) when all demographic variables were adjusted for.

Flowchart of study subject selection

Conclusion

Diagnosis of COVID-19 was not significantly associated with development of AA even after appropriately adjusting for covariates.

Disclosures

All Authors: No reported disclosures

353. New-Onset Diabetes as an Acute Complication of COVID-19: A National Population Cohort Analysis

Background

Diabetes is emerging as one of the complications of coronavirus disease 2019 (COVID-19), but this is hard to be revealed with cross-sectional studies since it is also known as the major predisposing factor for high-risk COVID-19. Therefore, this study aimed to estimate the risk of new-onset diabetes after COVID-19 through a population follow-up study.

Methods

All COVID-19 confirmed cases in Korea from January 20 to June 4, 2020, were matched with national health insurance data and their health screening data, both provided by the National Health Insurance Service of Korea. Controls were selected as the people who received the PCR test for COVID-19 and showed negative results in the same period and followed up until July 19, 2020. We selected the outcome as the diagnosis of diabetes according to the 10th revision of the International Statistical Classification of Diseases and Related Health Problems (ICD-10, E10 – E14). People who were diagnosed with diabetes in the past five years were excluded from both groups. After performing a log-rank test between groups, adjusted incidence rate and hazard ratio were estimated using Cox proportional hazard modeling. Demographic characteristics (age, sex, region, family histories of hypertension/diabetes, and income) and underlying health conditions such as hypertension, dyslipidemia, heart disease, alcohol consumption, cigarette smoking, and BMI were adjusted. Proportional assumptions were tested by the zph test and the sensitivity analysis by excluding each factor in turn and comparing results.

Results

A total of 6,247 COVID-19 patients and 143,594 controls without diabetes in the past were included for the analysis. The number of new-onset diabetes were 759 (12.15%) in COVID-19 patients and 3,465 (2.41%) in controls (P < 0.01). The adjusted incidence of diabetes was 15.34 (95% confidence interval, CI: 14.10 – 16.66) and 11.18 (95% CI: 10.67 – 11.72) per 100 person-year, respectively, with the mean follow-up time as 46.31 (standard deviation: 16.37) days. The adjusted hazard ratio of diabetes in COVID-19 cases was 2.97 (95% CI: 2.44 – 3.63).

Conclusion

Since COVID-19 patients showed a higher incidence of new-onset diabetes in a short-time follow-up, we should consider diabetes as one of the possible complications of COVID-19.

Disclosures

All Authors: No reported disclosures

1442. Spatiotemporal Clusters of Varicella and the Regional Risks through Bayesian Approach: A National Five-year Cohort Analysis

Background

Since varicella epidemics repeatedly occurred in Korea, it is essential to control varicella outbreaks preemptively in the targeted region. Therefore, we aimed to reveal spatiotemporal clusters of varicella and the regional risk factor of varicella incidence at the national level.

Methods

All varicella cases (defined as ICD-10 codes, B01-B09) from 2013 to 2017 in Korea were extracted from National Health Insurance Service. Of the total, 566,978 cases were realigned spatially by 250 administrative districts of Korea and temporally by a week. Spatial autocorrelation was tested using the global Moran’s I statistics using Monte Carlo simulation. Kulldorff’s prospective space-time scan statistics were used to reveal space-time clusters of varicella. Possible risk factors were extracted from the Korean Statistical Information Service and Community Health Survey of Korea, including hand hygiene perceptions, alcohol and smoking status, the proportion of children under 15 years old, the number of households, and household income by regions. After selecting significant risk factors through non-spatial generalized linear models, a conditional autoregressive spatiotempoal model with Bayesian extension was applied to estimate the regional factors affecting varicella incidence.

Results

There was spatial autocorrelation using Global Moran’s I statistics (P&lt; 0.01). When the maximum cluster size was limited to 10% of the population, 17 spatiotemporal clusters were detected in specific regions in Korea (figure 1). Low perception of hand hygiene, the high proportion of alcohol drinking and cigarette smoking, high children proportion, low number of familial member, and low household income were associated with varicella spatiotemporal incidence (odds ratio: 0.97, 1.01, 2.31, 1.10, 0.99, 0.99, respectively; 95% credible intervals of all risk factors did not include 1).

Figure 1. Space-time prospective clusters of varicella in Korea using varicella incidence from 2013 to 2017.

Conclusion

Varicella incidence shows spatiotemporal clustering patterns in specific regions. Since regional factors such as the perception rate of hand hygiene, child proportion, alcohol drinking, cigarette smoking, and low household income affect varicella’s spatiotemporal incidence, strategies for targeted control of high-risk regions are strongly recommended.

Disclosures

All Authors: No reported disclosures

Spatial epidemiologic analysis of the liver cancer and gallbladder cancer incidence and its determinants in South Korea

BACKGROUND

There have been reports on regional variation in prevalence of hepatitis B and C, and Clonorchis sinensis (C. sinensis) infection, which indicates potential of spatial variation in liver cancer and gallbladder cancer incidence in Korea. Therefore, we aimed to assess the regional variation of liver and gallbladder cancer incidence and its determinants based on the regional distribution of risk factors, including hepatitis B infection in Korea.

METHODS

This study used an ecological study design and district-level cancer incidence statistics generated by the National Cancer Center. Spatial clusters of liver and gallbladder cancer incidence were detected based on spatial scan statistics using SaTScan™ software. We set the size of maximum spatial scanning window of 25 and 35% of the population at risk for analyses of liver and gallbladder cancer, respectively. Significance level of 0.05 was used to reject the null hypothesis of no cluster. We fitted the Besag-York-Mollie model using integrated nested Laplace approximations to assess factors that influence the regional variation in cancer incidence.

RESULTS

Spatial clusters with high liver cancer incidence rates were detected in the southwestern and southeastern regions of Korea. High gallbladder cancer incidence rates are clustered in the southeastern region. Regional liver cancer incidence can be accounted for the prevalence of high household income (coefficient, - 0.10; 95% credible interval [CI], - 0.18 to - 0.02), marital status (coefficient, - 0.14; 95% CI, - 0.25 to - 0.03), the incidence of hepatitis B (coefficient, 0.87; 95% CI, 0.29 to 1.44), and liver cancer screening (coefficient, 0.06; 95% CI, 0.00 to 0.12), while gallbladder cancer incidence was related to the prevalence of high household income (coefficient, - 0.03; 95% CI, - 0.05 to 0.00) and living close to a river with a high prevalence of liver fluke infection (coefficient, 0.55; 95% CI, 0.14 to 0.96).

CONCLUSIONS

This study demonstrated geographic variation in liver and gallbladder cancer incidence, which can be explained by determinants such as hepatitis B, income, marital status, and living near a river.

Real-world experience of how chlorhexidine bathing affects the acquisition and incidence of vancomycin-resistant enterococci (VRE) in a medical intensive care unit with VRE endemicity: a prospective interrupted time-series study

BACKGROUND

Critically ill patients in intensive care units (ICUs) often acquire opportunistic infections or are colonized by vancomycin-resistant enterococci (VRE), which limits therapeutic options and results in high case-fatality rates. In clinical practice, the beneficial effects of universal chlorhexidine gluconate (CHG) bathing on the control of VRE remain unclear. This study aimed to investigate whether 2% CHG daily bathing reduced the acquisition of VRE in the setting of a medical ICU (MICU) with VRE endemicity.

METHODS

This quasi-experimental intervention study was conducted in a 23-bed MICU of a tertiary care hospital in Korea from September 2016 to December 2017. In a prospective, interrupted time-series analysis (ITS) with a 6-month CHG bathing intervention, we compared the acquisition and incidence of VRE and the incidence of methicillin-resistant Staphylococcus aureus (MRSA) and carbapenem-resistant Acinetobacter baumannii (CRAB) between the pre-intervention and intervention periods. The primary and secondary outcomes were a change in the acquisition of VRE and incidence of VRE, MRSA, or CRAB between the two periods, respectively.

RESULTS

All the adult patients admitted to the MICU were enrolled in the pre-intervention (n = 259) and intervention (n = 242). The overall CHG daily bathing compliance rate was 72.5%. In the ITS, there was a significant intervention effect with a 58% decrease in VRE acquisition (95% CI 7.1-82.1%, p = 0.038) following the intervention. However, there was no significant intervention effects on the incidence trend of VRE, MRSA, and CRAB determined by clinical culture between the pre-intervention and intervention periods.

CONCLUSION

In this real-world study, we concluded that daily bathing with CHG may be an effective measure to reduce VRE cross-transmission among patients in MICU with a high VRE endemicity.

Epidemiology and Regional Predictors of COVID-19 Clusters: A Bayesian Spatial Analysis Through a Nationwide Contact Tracing Data

Purpose: Revealing the clustering risks of COVID-19 and prediction is essential for effective quarantine policies, since clusters can lead to rapid transmission and high mortality in a short period. This study aimed to present which regional and social characteristics make COVID-19 cluster with high risk. Methods: By analyzing the data of all confirmed cases (14,423) in Korea between January 10 and August 3, 2020, provided by the Korea Disease Control and Prevention Agency, we manually linked each case and discovered clusters. After classifying the cases into clusters as nine types, we compared the duration and size of clusters by types to reveal high-risk cluster types. Also, we estimated odds for the risk factors for COVID-19 clustering by a spatial autoregressive model using the Bayesian approach. Results: Regarding the classified clusters (n = 539), the mean size was 19.21, and the mean duration was 9.24 days. The number of clusters was high in medical facilities, workplaces, and nursing homes. However, multilevel marketing, religious facilities, and restaurants/business-related clusters tended to be larger and longer when an outbreak occurred. According to the spatial analysis in COVID-19 clusters of more than 20 cases, the global Moran's I statistics value was 0.14 (p < 0.01). After adjusting for population size, the risks of COVID-19 clusters were related to male gender (OR = 1.29) and low influenza vaccination rate (OR = 0.87). After the spatial modeling, the predicted probability of forming clusters was visualized and compared with the actual incidence and local Moran's I statistics 2 months after the study period. Conclusions: COVID-19 makes different sizes of clusters in various contact settings; thus, precise epidemic control measures are needed. Also, when detecting and screening for COVID-19 clusters, regional risks such as vaccination rate should be considered for predicting risk to control the pandemic cost-effectively.

Spatiotemporal risk assessment for avian influenza outbreak based on the dynamics of habitat suitability for wild birds

Highly pathogenic avian influenza (HPAI) has predominantly damaged the poultry industry worldwide. The fundamental prevention and control strategy for HPAI includes early detection and timely intervention enforcement through a systematic surveillance system for wild birds based on the ecological understanding of the dynamics of wild birds' movements. Our study aimed to develop a spatiotemporal risk assessment model for avian influenza (AI) infection in wild birds to empower surveillance information for a contingency strategy. For this purpose, first, we predicted the monthly habitat suitability of seven waterfowl species, using 227,671 Global Positioning System (GPS) tracking records of 562 birds from 2014 to 2018 in the Republic of Korea (ROK). Then, that predicted habitat suitability and 421 coordinates of AI detection sites in wild birds were used to build the risk assessment model. Subsequently, we compared the monthly predicted risk of avian influenza virus (AIv) identification in wild birds between case and non-case poultry farms with HPAI H5N6 outbreak in the ROK between 2016 and 2017. The results reported considerable variation of monthly habitat suitability of seven waterfowls and the impact of predicting AI occurrences in wild birds. The high habitat suitability for spot-billed ducks (contribution rate in November = 40.9%) and mallards (contribution rate in January = 34.3%) significantly contributed to predicting the average risk of AIv identification in wild birds, with high predictive performance [the monthly mean of area under the curve (AUC) = 0.978]. Moreover, our model showed that the averaged risk of identification AI in wild birds was significantly higher in HPAI infected premises, with infected domestic duck holdings exhibiting a significantly higher risk than the chicken farms in November. This study suggests that animal health authority establishes a risk-based HPAI surveillance system grounded on the ecological nature of wild birds to improve the effectiveness of prevention and preparedness of emerging epidemics.

Lack of Evidence of COVID-19 Being a Risk Factor of Alopecia Areata: Results of a National Cohort Study in South Korea

Background: Concerns about alopecia areata (AA) in coronavirus disease 2019 (COVID-19) patients have emerged among dermatologists. However, most of the extant kinds of literature have limited implications by relying on cross-sectional studies with restricted study subjects without the control group. Objective: Our study aims to investigate the risk of developing AA among COVID-19 patients in South Korea using national representative data. Methods: We used the National Health Insurance Service COVID-19 cohort database, comprising COVID-19 patients and the control group, all of whom were diagnosed from January 1, 2020, to June 4, 2020. Patients were defined as individuals who were confirmed as COVID-19 positive, regardless of disease severity. Controls were defined as those who were confirmed as COVID-19 negatives. People with a history of AA during the period 2015-2019 were excluded. The primary endpoint was a new diagnosis of AA (ICD-10-Code: L63). The adjusted incidence rate ratio (IRR) of developing AA was estimated using a log-link Poisson regression model based on incidence density. The model adjusted for (1) age and sex and (2) demographic variables (age, sex, place of residence, and income level). Results: A total of 226,737 individuals (7,958 [3.5%] cases and 218,779 [96.5%] controls) were included in the final analysis. The ratio of newly diagnosed AA was 18/7,958 (0.2%) in cases and 195/218,779 (0.1%) in controls. IRRs of COVID-19 patients having newly diagnosed AA compared to controls were 0.78 (95% CI: 0.48-1.27) when age and sex were adjusted for and 0.60 (95% CI: 0.35-1.03) when all demographic variables were adjusted for. Conclusion: Diagnosis of COVID-19 was not significantly associated with the development of AA even after appropriately adjusting for covariates.

Association between companion animal ownership and overall life satisfaction in Seoul, Korea

This study aimed to analyze the association between companion animal ownership, the sub-factors of this ownership (the species and number of owned pets), and overall life satisfaction (OLS). Data was obtained from the publicly available responses to the 2017 Seoul Survey, conducted among Seoul-based Korean locals aged ≥ 15 years (N = 42,687; pet owners = 8,708, non-owners = 33,979). Propensity score was calculated by performing logistic regressions with covariates and data was matched using the nearest-neighbor method. Further, multiple linear regression was performed to analyze this association using the matched data. Additionally, survey-weighted multiple regressions were performed: 1) within pet owners, and 2) after stratifying owners with the number of pets owned. Pet owners in Seoul, South Korea reported higher levels of OLS than non-owners, even after controlling for covariates-age, sex, marital status, family size, family income, job, education, types of housing, housing tenure. Owners with both dogs and cats showed the highest average OLS scores (owners with 2 pets: Mean [M] = 58.05, Standard Deviation [SD] = 0.67; owners with ≥ 3 pets: M = 59.03, SD = 1.02), followed by single pet owners of either a cat (M = 56.64, SD = 0.37) or a dog (M = 56.14, SD = 0.13). Single pet owners reported significantly higher levels of OLS than those with 2 or ≥ 3 pets when pet types were adjusted for. When owners had a single pet, pet types (dog or cat) did not generate a significant difference in OLS scores. Among owners with 2 or ≥ 3 pets, however, owners with both dogs and cats had higher OLS scores than dog owners. This research has significant implications for promoting future study on companion animal effects for improving human health and well-being. Mechanisms of the effect, including cultural factors, should be further investigated.

Factors associated with the difference between the incidence and case-fatality ratio of coronavirus disease 2019 by country

Coronavirus disease (COVID-19) has been spreading all over the world; however, its incidence and case-fatality ratio differ greatly between countries and between continents. We investigated factors associated with international variation in COVID-19 incidence and case-fatality ratio (CFR) across 107 northern hemisphere countries, using publicly available COVID-19 outcome data as of 14 September 2020. We included country-specific geographic, demographic, socio-economic features, global health security index (GHSI), healthcare capacity, and major health behavior indexes in multivariate models to explain this variation. Multiple linear regression highlighted that incidence was associated with ethnic region (p < 0.05), global health security index 4 (GHSI4) (beta coefficient [β] 0.50, 95% Confidence Interval [CI] 0.14-0.87), population density (β 0.35, 95% CI 0.10-0.60), and water safety level (β 0.51, 95% CI 0.19-0.84). The CFR was associated with ethnic region (p < 0.05), GHSI4 (β 0.53, 95% CI 0.14-0.92), proportion of population over 65 (β 0.71, 95% CI 0.19-1.24), international tourism receipt level (β - 0.23, 95% CI - 0.43 to - 0.03), and the number of physicians (β - 0.37, 95% CI - 0.69 to - 0.06). Ethnic region was the most influential factor for both COVID-19 incidence (partial [Formula: see text] = 0.545) and CFR (partial [Formula: see text] = 0.372), even after adjusting for various confounding factors.

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.

1499Health behaviours as risk factors of COVID-19 incidence in South Korea

Background

Personal health behaviours, which rely on community characteristics, could affect individual vulnerability on disease infection. Due to insufficient study to examine health behaviours as risk factors of COVID-19 infection, we conducted municipal level spatial analysis to investigate association between health behaviours and COVID-19 incidence.

Methods

We extracted cumulative COVID-19 incidence data from January 20^th 2020 to February 25^th 2021, health behaviours, health condition, socio-economic factors, and covariates in municipal level from publicly available dataset. We chose variables, which were standardized, considering multicollinearity (VIF<10). Further, we employed bayesian hierarchical negative binomial model with intrinsic conditional autoregressive (iCAR) and Besag, York and Mollié (BYM) model, and used deviance information criterion (DIC) for final model selection.

Results

The mean cumulative COVID-19 incidence per 10,000 population among 229 municipality was 13.73 (Standard deviation=11.43). iCAR model (DIC=2,825.3) outperformed BYM model (DIC=14,009.4). The results of iCAR model highlighted that incidence was associated with dental hygiene practice (incidence risk ratios [IRR]=0.92, 95% Credible Interval [CI]=0.85–1.00), whether tried to be thin (IRR=1.10, 95% CI = 1.00–1.20), proportion of medical personnel (IRR=1.09, 95% CI = 1.01–1.17), and volume of public transportation (IRR=1.19, 95% CI = 1.05–1.35), even after adjusting for various confounding factors.

Conclusions

Municipality with lower cumulative incidence was likely to have more people who practiced to keep dental hygiene and less people who tried to be thin.

Key messages

Municipal level spatial analysis resulted that health behaviours were associated with COVID-19 incidence in South Korea.

1001Spatio-temporal epidemiology of mumps and related region factors in Korea

Background

Mumps is in Korea's national immunization program, though there are still epidemics, especially in young age. The study's objectives are to establish the epidemiological characteristics of mumps and suggest the predicting factors.

Methods

We extracted cases from national health insurance data, between 2013 and 2017. Age-specific incidence rate and geographical distribution were evaluated. We tested for spatial autocorrelation by Moran’s I statistics with Delaunary triangular links. Simultaneous autoregressive model for cumulative incidence of mumps using triangular links was used to predict cumulative incidence with region specific factors.

Results

A total of 219,149 (85.12 per 100,000) were diagnosed and 23,805 (9.25 per 100,000) were hospitalized. Weekly cumulative incidence showed two epidemics every year, between weeks 20-25 and 40-45. Cumulative incidence of ages 10-19 was the highest, 332.21 per 100,000 people, followed by 300.75 per 100,000 people in ages 0-9. Geographical distribution showed clusters of epidemics, and Moran’s I statistics was 0.304 with a p-value &lt;0.01. The Simultaneous autoregressive model estimated the mean age and hospital resources of each region as prediction factors for geographical distribution of mumps.

Conclusions

Mumps is common in children and peaks in summer and winter. Additionally, there are geographical clusters in epidemics, and the effect of region factors such as mean age and hospital resources are suspected.

Key messages

Two peaks in age and season appear in mumps in Korea. Clusters of geographical distribution indicate that region factors may affect the incidence.

1472Spatial clusters and affecting factors on Alzheimer's disease death in South Korea

Background

The prevalence of dementia is increasing worldwide; and dementia deaths are also increasing. In South Korea, deaths from Alzheimer's disease (AD) ranked 9th in the 2018 cause of death statistics, and the ranking has risen.

Methods

We collected 2009 to 2018 AD deaths and related data from Statistics Korea and Community Health Survey. SaTScan software was used for detecting and evaluating the clusters with high risk in AD deaths, and R version 4.0.3 was used for mapping and analysis of affecting factors.

Results

A total of 39,412 people died from AD during 10 years in Korea, 7.7 per 100,000 inhabitants. While 98.7% of deaths were above-65 age, the proportion of under 65 was also rising. The global Moran index of 10 years’ AD deaths was 0.2 (P &lt; 0.01), and the clusters were detected primarily in southern rural region. According to the spatial regression analysis, AD deaths in 2018 were increased in area with lower dementia screening rate, long-term care workers, and higher home-care service usage rate in long-term care, inhabitants educated about dementia.

Conclusions

Some clusters of AD deaths were identified, and they were influenced by institutional factors. It is necessary that the local government considers characteristics of each region when implementing the dementia policies.

Key messages

AD deaths in South Korea were increasing from 2009 to 2018, and their clusters were observed in southern regions. AD deaths in 2018 were influenced by dementia-related policies.

1003Modifiable risk factors and incidence of diabetes mellitus progressing in the prediabetic Population

Background

Although the prevention of diabetes mellitus is important, factors related to its progression in the prediabetic population are rarely revealed. This study aimed to estimate the rate of progression and uncover the modifiable risk factors leading to progression.

Methods

We constructed a group from the National Health Screening Cohort, consisting of adults who received national health screening tests in 2002. After selecting a prediabetic population, we classified them into two groups based on their diabetes progression after a 13-year follow up. The adjusted incidence rate was estimated, and the Cox proportional hazard modelling was performed to identify risk factors for progression.

Results

The progression rate of diabetes in the prediabetic population (88,330) was 22.85% (20,184), with an adjusted incidence rate of 25.18 (95% confidence interval, CI: 24.44 – 26.02) per 1,000 person-year, ages 40-64 and 25.69 (95% CI: 24.46 – 26.95) in those 65 or older. Among modifiable risk factors, smoking showed the highest hazard ratio, 1.21 (95% CI: 1.16 – 1.25), followed by BMI and alcohol consumption with hazard ratios of 1.06 (95% CI: 1.06 – 1.07) and 1.06 (95% CI: 1.02 – 1.09), respectively.

Conclusions

Considering the high progression rate of the prediabetic population, modifiable risk factors, such as smoking, should be managed.

Key messages

The progression rate of the prediabetic population was 25–26% per 1,000 person-year. At the 13-year follow up, modifiable risk factors, such as smoking, BMI, and alcohol consumption, affected the prediabetic population.

1496Spatiotemporal patterns of Kawasaki disease in South Korea: using 2008-2017 national representative data

Background

Despite the etiology of Kawasaki Disease (KD) remains unknown, identifying spatiotemporal clusters of KD could support its hypothesis to be infectious disease. However, spatiotemporal clusters of KD have never been reported in South Korea. Therefore, this study aims to analyse the spatiotemporal patterns of KD in South Korea using national representative data.

Methods

We extracted epidemiologic-week (Epi-week) based KD case (ICD-10-CM code, M303) from 2008-2017 national health insurance service data in municipal level. To determine whether spatial autocorrelation and municipal-level clusters exist, year, sex, and age group (&lt;5, 5-9) stratified Global Moran’s I statistics and LISA spatial scan statistics on KD incidence were conducted.

Results

A total of 98,503 cases of KD were reported in 2008-2017 (aged &lt;5: 72,562 cases [73.7%]). Mean diagnosis age was 4.2±7.0 years, and male-to-female ratio was 1.39:1. Incidence among patients aged &lt;5 increased since 2008; the highest in 2016 (396.78 per 100,000 population). KD had seasonality of winter and summer. Epi-week 46-52 was the most frequent season for cases aged &lt;5, while Epi-week 1-5 was the most frequent season for cases aged 5-9. Positive spatial autocorrelation was consistently reported in every stratum except for ‘2012year/female/age5-9’ and ‘2015year/female/age5-9’ stratum. High-high clusters were consistently detected in the eastern part of South Korea in every stratum.

Conclusions

South Korea had steady increase in KD incidence since 2008 and municipal-level clusters throughout 2008-2017.

Key messages

Kawasaki disease in South Korea had spatiotemporal patterns.

Trends in Viral Respiratory Infections During COVID-19 Pandemic, South Korea

We compared weekly positivity rates of 8 respiratory viruses in South Korea during 2010-2019 and 2020. The overall mean positivity rate for these viruses decreased from 54.7% in 2010-2019 to 39.1% in 2020. Pandemic control measures might have reduced the incidence of many, but not all, viral respiratory infections.

Effect of diurnal temperature range on emergency room visits for acute upper respiratory tract infections

Background

An acute upper respiratory tract infection (URI) is the most common disease worldwide, irrespective of age or sex. This study aimed to evaluate the short-term effect of diurnal temperature range (DTR) on emergency room (ER) visits for URI in Seoul, Korea, between 2009 and 2013.

Methods

Daily ER visits for URI were selected from the National Emergency Department Information System, which is a nationwide daily reporting system for ER visits in Korea. URI cases were defined according to International Classification of Diseases, 10^thRevision codes J00–J06. The search for DTR effects associated with URI was performed using a semi-parametric generalized additive model approach with log link.

Results

There were 529,527 ER visits for URI during the study period, with a daily mean of 290 visits (range, 74–1942 visits). The mean daily DTR was 8.05 °C (range, 1.1–17.6 °C). The cumulative day (lag 02) effect of DTR above 6.57 °C per 1 °C increment was associated with a 1.42% (95% confidence interval [CI] 0.04–2.82) increase in total URI. Children (≤ 5 years of age) were affected by DTR above 6.57 °C per 1 °C, with 1.45% (95% CI 0.32–2.60) at lag 02, adults (19–64 years) with 2.77% (95% CI 0.39–5.20) at lag 07. When the DTR (lag02) was 6.57 °C to 11.03 °C, the relative risk was significant at 6.01% (95% CI 2.45–9.69) for every 1 °C increase in youth subjects aged for 6 to 18 years.

Conclusions

DTR was associated with a higher risk for ER visits for URI. In addition, the results suggested that the lag effects and relative risks of DTR on URI were quite different according to age.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12199-021-00974-w.

Effect of Seawater Temperature Increase on the Occurrence of Coastal Vibrio vulnificus Cases: Korean National Surveillance Data from 2003 to 2016

The purpose of this study was to assess the association between seawater temperature and Vibrio vulnificus cases in coastal regions of Korea. All V. vulnificus cases in coastal regions notified to the Korea Disease Control and Prevention Agency between 2003 and 2016 were included in this work. Data for seawater temperature on the south, west, and east coast during the study period were provided by the Korea Oceanographic Data Center of the National Institute of Fisheries Science. We used a generalized additive model and performed a negative binomial regression analysis. In total, 383 notified cases were analyzed (west coast: 196 cases, south coast: 162, and east coast: 25). The maximum seawater temperature was the most significant predictor of V. vulnificus cases on the south and east coasts (relative risk according to the 1 °C increase in seawater temperature (RR) = 1.35 (95% confidence interval (CI): 1.19–1.53) and 1.30 (95% CI: 1.06–1.59), respectively). However, the mean seawater temperature was the most significant predictor for the west coast (RR = 1.34 (95% CI: 1.20–1.51)). These results indicate that continuously monitoring seawater temperature increase in each coastal area is crucial to prevent V. vulnificus infections and protect high-risk groups, such as persons with liver disease.

Paradoxical health care utilization patterns among children in Korea who did not receive mandatory pneumococcal vaccination

BACKGROUND

Unvaccinated children in the National Immunization Program (NIP) are a public health concern. We used Korean national population data to analyze health care utilization patterns of NIP-eligible children and identify the unvaccinated group.

METHODS

Pneumococcal vaccination (PCV) records were reviewed to determine the vaccination status of children born between 2013 and 2015. Children who received three doses or more from a 3 + 1 schedule were defined as vaccinated, while those who had not received any pneumococcal vaccinations were defined as unvaccinated. Corresponding health care utilization records were retrieved from the National Health Insurance Review and Assessment Service. The incidence of combined pneumococcal infections and health care utilization rates were estimated and the proportion of complementary and alternative medicine (CAM) utilization among the total health care utilization records was measured.

RESULTS

In total, 26,893 (2.1%) of 1,272,685 children remained unvaccinated. The incidence of pneumococcal infection was lower in unvaccinated children, at 10.1 cases (9.8-10.3) per 1000 person-months. However, their health care utilization was significantly lower than that noted for vaccinated children (hospital visit rate: 26.6 (95% confidence interval [CI] 26.5-26.7) vs. 3.2 (3.2-3.3) visits annually), indicating underdetection. CAM treatment was sought at least three times often more in unvaccinated children than in vaccinated children (3.5% vs. 1.1%).

CONCLUSION

Unvaccinated children showed significantly lower utilization of overall health care than the vaccinated children; however, a higher preference for CAM was noted among unvaccinated children than among vaccinated children. These differences in care-seeking patterns should be considered when identifying unvaccinated children and providing protection through vaccination programs.

A longitudinal analysis of the progression from normal blood pressure to stage 2 hypertension: A 12-year Korean cohort

Background

The study aimed to estimate the incidence of and period of progression to stage 2 hypertension from normal blood pressure.

Methods

We selected a total of 21,172 normotensive individuals between 2003 and 2004 from the National Health Insurance Service-Health Screening and followed them up until 2015. The criteria for blood pressure were based on the American College of Cardiology/American Heart Association 2017 guideline (normal BP: SBP < 120 and DBP < 80 mmHg, elevated BP: SBP 120–129 and DBP < 80 mmHg, stage 1 hypertension: SBP 130–139 or DBP 80–89 mmHg, stage 2 hypertension: SBP ≥140 or DBP ≥ 90 mmHg). We classified the participants into four courses (Course A: normal BP → elevated BP → stage 1 hypertension→ stage 2 hypertension, Course B: normal BP → elevated BP → stage 2 hypertension, Course C: normal BP → stage 1 hypertension → stage 2 hypertension, Course D: normal BP → stage 2 hypertension) according to their progression from normal blood pressure to stage 2 hypertension.

Results

During the median 12.23 years of follow-up period, 52.8% (n= 11,168) and 23.6% (n=5004) of the participants had stage 1 and stage 2 hypertension, respectively. In particular, over 60 years old had a 2.8-fold higher incidence of stage 2 hypertension than 40–49 years old. After the follow-up period, 77.5% (n=3879) of participants with stage 2 hypertension were found to be course C (n= 2378) and D (n=1501). After the follow-up period, 77.5% (n=3879) of participants with stage 2 hypertension were found to be course C (n= 2378) and D (n=1501). The mean years of progression from normal blood pressure to stage 2 hypertension were 8.7±2.6 years (course A), 6.1±2.9 years (course B), 7.5±2.8 years (course C) and 3.2±2.0 years, respectively.

Conclusions

This study found that the incidence of hypertension is associated with the progression at each stage. We suggest that the strategies necessary to prevent progression to stage 2 hypertension need to be set differently for each target course.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-020-10115-7.

Association of Anopheles sinensis average abundance and climate factors: Use of mosquito surveillance data in Goyang, Korea

Malaria is a vector-borne disease transmitted by Anopheline mosquitoes. In Korea, Plasmodium vivax malaria is an endemic disease and the main vector is Anopheles sinensis. Plasmodium vivax malaria is common in the northwestern part of South Korea, including in the city of Goyang in regions near the demilitarized zone. This study aimed to identify the best time-series model for predicting mosquito average abundance in Goyang, Korea. Mosquito data were obtained from the Mosquito Surveillance Program of the Goyang Ilsanseogu Public Health Center for the period 2008–2012. Black light traps were set up periodically in a park, a senior community center, and a village community center, public health center, drainage pumping station, cactus research center, restaurant near forest, in which many activities occur at night. In total, 9,512 female mosquitoes were collected at 12 permanent trapping sites during the mosquito season in the study period. Weekly An. sinensis average abundance was positively correlated with minimum grass temperature (r = 0.694, p < 0.001), precipitation (r = 0.326, p = 0.001). The results showed that seasonal autoregressive integrated moving average (SARIMA) (1,0,0)(0,0,1)₂₁ with minimum grass temperature variable at time lag0 weeks and the precipitation variable at time lag1 weeks provided that best model of mosquito average abundance. The multivariate model accounted for about 54.1% of the mosquito average abundance variation. Time-series analysis of mosquito average abundance and climate factors provided basic information for predicting the occurrence of malaria mosquitoes.

The Serial Interval of COVID-19 in Korea: 1,567 Pairs of Symptomatic Cases from Contact Tracing

Although coronavirus disease 2019 (COVID-19) is an ongoing pandemic, the mean serial interval was measured differently across nations. Through the Korean national COVID-19 contact tracing system, we were able to investigate personal contacts in all symptomatic cases in Korea from January 20 to August 3, 2020. The mean serial interval was calculated by the duration between the symptom onset of the infector and infectee, and became shorter after the case definition changed to include not-imported cases in Korea on February 20, 2020. The mean serial interval before and after this fifth case definition was 6.12 and 3.93 days based on the infectors' symptom onset date, respectively, and 4.02 days in total with the median of 3 days. Older age and women lead to longer serial intervals.

Incidence and risk factors of vascular complications in people with impaired fasting glucose: a national cohort study in Korea

This study aimed to evaluate the risk of vascular complications of impaired fasting glucose (IFG). This population-based study included 425,608 participants from the National Health Screening Cohort in Korea in 2003 and 2004 who were followed-up until 2015. The participants were classified into normal, IFG, and diabetes groups based on fasting plasma glucose levels. Incidence rate (per 1000 person-year) was evaluated for the following vascular complications: cardiovascular (ischemic heart disease, cerebrovascular disease, arterial and capillary disease), renal, and retinal diseases. Hazard ratios (HR) of IFG for diabetes were estimated after adjusting for patient characteristics. Among the 88,330 IFG participants, the incidence of cardiovascular, chronic renal and retinal diseases were 11.52, 0.47, and 1.08 per 1000 person-years, respectively. Furthermore, IFG patients with a family history of diabetes, past history of hypertension, and high body mass index had significantly increased risk of vascular complications [adjusted HR, cardiovascular: 1.39 (95% CI 1.33–1.46); renal: 2.17 (95% CI 1.66–2.83); and retinal: 1.14 (95% CI 0.98–1.32)]. IFG patients have a substantial risk of cardiovascular, chronic renal and retinal diseases. Therefore, early preventative interventions are beneficial, especially for those with high-risk factors, in whom should emphasize on maintaining a healthy lifestyle, early screening and continuous follow-up.

OCCUPATIONAL RADIATION PROCEDURES AND DOSES AMONG NURSES IN SOUTH KOREA

This study investigated occupational radiation procedures and radiation exposures among nurses in South Korea. A total of 530 nurses were surveyed from 2012 to 2013, and the survey data were linked with the dosimetry data. Multiple regression analysis was used to identify the factors associated with radiation dose. The most frequent procedure performed by the nurses was interventional radiology, followed by fluoroscopy and routine X-ray. The average annual effective dose and the cumulative dose were 0.91 mSv and 4.66 mSv, respectively. Characteristics of nurses exposed to high radiation doses were male, completed graduate school or higher, first worked before 2000 and performing interventional procedures, nuclear medicine test and fluoroscopy. Performing nuclear medicine tests and interventional procedures had a significant positive association with high radiation exposure.

Cost effectiveness of trivalent and quadrivalent influenza vaccines in 50- to 64-year-old adults in Korea

BACKGROUND

Influenza causes severe complications in at-risk populations, resulting in significant morbidity and mortality. Vaccination is the most effective measure to prevent infection and complications caused by seasonal influenza. However, no study has analyzed the cost-effectiveness of influenza vaccines in 50- to 64-year-olds in South Korea.

OBJECTIVE

We examined the application of the National Immunization Program (NIP) in 50- to 64-year-olds and compared the cost-effectiveness of quadrivalent influenza vaccine (QIV) with that of trivalent influenza vaccine (TIV) in South Korea.

METHODS

One-year static model was assumed by constructing separate decision trees for age subgroups: 50-54, 55-59, and 60-64. Each subgroup was divided into at-risk and not-at-risk groups. Using circulation data from previous studies and Korea Centers for Disease Control and Prevention, we estimated the probabilities of influenza infection, outpatient treatment, hospitalization, and deaths. Medical cost was estimated from 2015 to 2017 National Health Insurance Sharing Service claim data, while productivity losses from work absenteeism or death were estimated from labor and economic surveys of Korean government. Disutility was estimated based on previous studies.

RESULTS

Compared with non-vaccination, incremental cost-effectiveness ratios (ICERs) for the 50-54, 55-59, and 60-64 age groups for TIV were US$2010.90, US$2004.58, and US$1865.55, respectively, while for QIV were US$2187.17, US$2190.89, and US$2074.52, respectively. Compared with TIV, ICERs for QIV were US$4445.66, US$4578.06, and US$4751.93, respectively. All the aforementioned ICER values were lower than the 2017 Korean GDP per capita of US$29,742.839.

CONCLUSION

Implementing the NIP in the 50- to 64-year-old age group was found to be cost effective. Since both TIV and QIV were cost effective, we recommend QIV as the preferred option, based on its greater protection against Influenza B.

Estimation of the Excess COVID-19 Cases in Seoul, South Korea by the Students Arriving from China

Background: In March 2020, overall, 37,000 international students from China, a country at risk of the 2019-novel coronavirus (COVID-19) infection has arrived in Seoul, South Korea. Individuals from the country at risk of COVID-19 infection have been included in the Korean home-quarantine program, but the efficacy of the program is uncertain. Methods: To estimate the possible number of infected individuals within the large influx of international students from China, we used a deterministic compartmental model for epidemic and performed a simulation-based search of different rates of compliance with home-quarantine. Results: Under the home-quarantine program, the number of the infected individuals would reach 40-72 from 12 March-24 March with the arrival of 0.2% of pre-infectious individuals. Furthermore, the number of isolated individuals would peak at 40-64 from 13 March-27 March in Seoul, South Korea. Our findings indicated when incoming international students showed strict compliance with quarantine, epidemics by the international student from China were less likely to occur in Seoul, South Korea. Conclusions: To mitigate possible epidemics, additional efforts to improve the compliance of home-quarantine of the individuals from countries with the virus risk are warranted along with other containment policies.

Risk factors of the progression to hypertension and characteristics of natural history during progression: A national cohort study

Background

Although the high disease burden that results from cardiovascular complications of hypertension, factors related to the progression to hypertension in the normotensive population are not actively reported. The purpose of this study was to estimate the rate of the progression to hypertension and to reveal the associated risk factors.

Methods

The study included normotensive participants from the National Health Insurance Service-National Health Screening Cohort, and contained a 10% sample of all adults who received a national health screening test in either 2002 or 2003. At the end of the study in 2015, the patients were divided into two groups based on whether or not they progressed to hypertension. Cox proportional hazard modeling was performed to identify risk factors for progression. Subgroup analysis using logistic regression was employed to reveal factors influencing the different natural history of the progression.

Results

Among the 75,335 included participants, the progression rate to hypertension was 66.39% (50,013), with an adjusted incidence rate of 8.62 per 100 person-year in the aged 40–64 group and 12.68 in the aged 65 or above group. Age, BMI, hemoglobin, and family history of hypertension and other diseases were related to the progression. Among the progression group, 78.21% (39,116) participants skipped a pre-hypertensive status; this group consisted of older females with lower pulse pressure and more alcohol consumption compared to people who had pre-hypertensive status before the progression.

Conclusion

Substantial risk factors for the progression to hypertension should be carefully managed even in normotensive participants who receive health screening tests.

An interim review of the epidemiological characteristics of 2019 novel coronavirus

OBJECTIVES

The 2019 novel coronavirus (2019-nCoV) from Wuhan, China is currently recognized as a public health emergency of global concern.

METHODS

We reviewed the currently available literature to provide up-to-date guidance on control measures to be implemented by public health authorities.

RESULTS

Some of the epidemiological characteristics of 2019-nCoV have been identified. However, there remain considerable uncertainties, which should be considered when providing guidance to public health authorities on control measures.

CONCLUSIONS

Additional studies incorporating more detailed information from confirmed cases would be valuable.

The epidemiological characteristics and spatio-temporal analysis of childhood hand, foot and mouth disease in Korea, 2011-2017

Objectives

Hand-foot-mouth disease (HFMD) is a common viral infection in children, with a significant disease burden due to its high contagion rate. This report studied the epidemiological characteristics as well as the chronological and geographical distribution of HFMD in children younger than 6 years of age in Korea.

Methods

This report established a database by integrating population and geographical data from health insurance claims for HFMD between 2011 and 2017, with an age restriction of ≤6 years, and explored the epidemiological characteristics of both HFMD patients and hospitalized cases in Korea. The relative risk ratio and spatio-temporal scan statistics were calculated by administrative district, using SaTScan.

Results

Over a 7-year period, 1,879,342 children under the age of 6 were diagnosed with HFMD (8.4 of 100 persons younger than 6 years of age). Seasonal incidence tended to increase from week 17 (May) peak between weeks 29 (July) and 39 (September), and increase rapidly in 1- to 2-year cycles. HFMD primarily occurred in children younger than 4 years of age. Furthermore, the greatest proportion of cases occurred at ages 1 (39.2%) and 2 (25.7%). Overall, 92.6% of all cases occurred before the age of 6. The proportion of cases before the age of 6was slightly higher in males. The timing of HFMD epidemics differed over the years. In 2015, the HFMD cumulative incidence was the lowest (5.5/1,000), and the spatio-temporal cluster (RR 2.32) was predominantly located south-central Korea, covering 65 counties for twenty-two weeks. In 2016, however, its cumulative incidence was high (RR 6.34) over a short period (11 weeks) in specific areas such as Ulsan, Daegu, Busan, and Gyeongnam. Also, the southern parts of Korea were found to have a higher rate of hospitalization.

Conclusions

HFMD in Korea is common in children younger than 6 years of age, and it tends to peak in the summer.