Nationwide Trends in Non-COVID-19 Infectious Disease Laboratory Tests in the Era of the COVID-19 Pandemic in Korea.

The coronavirus disease 2019 pandemic has brought significant changes to infectious disease management globally. This study explored changes in clinical microbiological testing trends and their implications for infectious disease incidence and medical utilization during the pandemic. We collected nationwide claims for monthly clinical microbiology tests from January 2018 to March 2022 using the National Health Insurance Service database. Seasonal autoregressive integrated moving average models were employed to make predictions for each disease based on the baseline period (January 2018 to January 2020). The results showed a significant decrease in general bacterial and fungal cultures, respiratory infectious disease-related, and inflammatory markers, while the representatives of tests for vector-borne diseases, healthcare-associated infections, and chronic viral infections remained stable. The study highlights the potential of clinical microbiological testing trends as an additional surveillance tool and offers implications for future infectious disease management and surveillance strategies in pandemic settings.

The Impact of Entry Restrictions on the Spread of Severe Acute Respiratory Syndrome Coronavirus Variants Between 2021 and 2022.

To contain the surge of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the South Korean government has implemented non-pharmacological interventions as well as border restrictions. The efficacy of entry restrictions should be evaluated to facilitate their preparation for new variants of SARS-CoV-2. This study explored the impact of border policy changes on overseas entrants and local cases of SARS-CoV-2 variants. Data from the Korea Disease Control and Prevention Agency randomly collected between April 11, 2021 and August 20, 2022 were evaluated using the Granger causality model. The results showed that the outbreak gap of delta variants between international and domestic cases was 10 weeks, while that of omicron variants was approximately 2 weeks, meaning that the quarantine policy helped contain delta variants rather than more transmissible variants. It is recommended that countries implement quarantine policies based on particular purposes accounting for the specific features of different variants to avoid potential negative impacts on the economy.

Relationship Between Coronavirus Disease 2019 Vaccination Rates and Rare But Potentially Fatal Adverse Events: A Regression Discontinuity Analysis of Western Countries.

BACKGROUND: Owing to limited experience with the new vaccine platforms, discussion of vaccine safety is inevitable. However, media coverage of adverse events of special interest could influence the vaccination rate; thus, evaluating the outcomes of adverse events of special interest influencing vaccine administration is crucial. METHODS: We conducted regression discontinuity in time analysis to calculate the local average treatment effect (LATE) using datasets from Our World in Data and Johns Hopkins University Center for Systems Science and Engineering. For the United States, the United Kingdom, and Europe, the cutoff points were April 23rd and June 23rd, April 7th, and the 14th week of 2021, respectively. RESULTS: The LATE of the Advisory Committee on Immunization Practices (ACIP) meeting held on April 23rd was -0.249 for all vaccines, -0.133 (-0.189 to -0.076) for Pfizer, -0.064 (-0.115 to -0.012) for Moderna, and -0.038 (-0.047 to -0.030) for Johnson & Johnson. Discontinuities were observed for all three types of vaccines in the United States. The June 23rd meeting of the ACIP (mRNA vaccines and myocarditis) did not convene any discontinuities. Furthermore, there was no significant drop in the weekly average vaccination rates in Europe following the European Medicines Agency (EMA) statement on April 7th. Conversely, there was a significant drop in the first-dose vaccination rates in the United Kingdom related to the EMA report. The first-dose vaccination rate for all vaccines changed by -0.104 (-0.176 to -0.032). CONCLUSION: Although monitoring and reporting of adverse events of special interest are important, a careful approach towards public announcements is warranted.

Model-informed COVID-19 exit strategy with projections of SARS-CoV-2 infections generated by variants in the Republic of Korea.

BACKGROUND: With the prompt administration of coronavirus disease 2019 (COVID-19) vaccines, highly vaccinated countries have begun to lift their stringent control measures. However, considering the spread of highly transmissible new variants, resuming socio-economic activities may lead to the resurgence of incidence, particularly in nations with a low proportion of individuals who have natural immunity. Here, we aimed to quantitatively assess an optimal COVID-19 exit strategy in the Republic of Korea, where only a small number of cumulative incidences have been recorded as of September 2021, comparing epidemiological outcomes via scenario analysis. METHODS: A discrete-time deterministic compartmental model structured by age group was used, accounting for the variant-specific transmission dynamics and the currently planned nationwide vaccination. All parameters were calibrated using comprehensive empirical data obtained from the Korea Disease Control and Prevention Agency. RESULTS: Our projection suggests that tapering the level of social distancing countermeasures to the minimum level from November 2021 can efficiently suppress a resurgence of incidence given the currently planned nationwide vaccine roll-out. In addition, considering the spread of the Delta variant, our model suggested that gradual easing of countermeasures for more than 4 months can efficiently withstand the prevalence of severe COVID-19 cases until the end of 2022. CONCLUSIONS: Our model-based projections provide evidence-based guidance for an exit strategy that allows society to resume normal life while sustaining the suppression of the COVID-19 epidemic in countries where the spread of COVID-19 has been well controlled.

Optimal Social Distancing Policy for COVID-19 Control in Korea: A Model-Based Analysis.

BACKGROUND: Since March 2020, when coronavirus disease 2019 (COVID-19) was declared a pandemic, many countries have applied unprecedented restrictive measures to contain the spread of the virus. This study aimed to explore the optimal social distancing policy for COVID-19 control in South Korea to safely reopen the society. METHODS: We developed an age-specific, deterministic compartment epidemic model to examine the COVID-19 control decision-making process, including the epidemiology of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) between 1 July 2021 and 30 December 2022. The model consists of the natural history of COVID-19, testing performance, vaccinations, and social distancing enforcement measures to detect and control SARS-CoV-2. We modelled potential intervention scenarios with three distinct components: 1) social distancing duration and level; 2) testing intensity; and 3) vaccination uptake rate. The primary and secondary outcomes were COVID-19 incidence and prevalence of severe patients requiring intensive care unit (ICU) care. RESULTS: Four (or more) months of social distancing (that can reduce 40-60% transmission) may mitigate epidemic resurgence and ICU demand in the future and keep the cases below the capacity limit if the testing intensity and vaccination rate remain constant or increase by 20% (with respect to the current level). In contrast, two months of strict social distancing enforcement may also successfully mitigate future epidemic surge and ICU demand as long as testing intensity and vaccination rates are increased by 20%. CONCLUSION: In South Korea, given the relatively high vaccination coverage and low incidence, four or more months of social distancing enforcement can effectively mitigate epidemic resurgence after lifting the social distancing measures. In addition, increasing the testing intensity and vaccination rate may help reduce necessary social distancing levels and duration to prevent a future epidemic resurgence and mitigate social and economic damage.

Model-based cost-effectiveness analysis of oral antivirals against SARS-CoV-2 in Korea.

OBJECTIVES: Many countries have authorized the emergency use of oral antiviral agents for patients with mild-to-moderate cases of coronavirus disease 2019 (COVID-19). We assessed the cost-effectiveness of these agents for reducing the number of severe COVID-19 cases and the burden on Korea's medical system. METHODS: Using an existing model, we estimated the number of people who would require hospital/intensive care unit (ICU) admission in Korea in 2022. The treatment scenarios included (1) all adult patients, (2) elderly patients only, and (3) adult patients with underlying diseases only, compared to standard care. Based on the current health system capacity, we calculated the incremental costs per severe case averted and hospital admission for each scenario. RESULTS: We estimated that 236,510 COVID-19 patients would require hospital/ICU admission in 2022 with standard care only. Nirmatrelvir/ritonavir (87% efficacy) was predicted to reduce this number by 80%, 24%, and 17% when targeting all adults, adults with underlying diseases, and elderly patients (25, 8, and 4%, respectively, for molnupiravir, with 30% efficacy). Nirmatrelvir/ritonavir use is likely to be cost-effective, with predicted costs of US$8,878, US$8,964, and US$1,454, per severe patient averted for the target groups listed above, respectively, while molnupiravir is likely to be less cost-effective, with costs of US$28,492, US$29,575, and US$7,915, respectively. CONCLUSIONS: In Korea, oral treatment using nirmatrelvir/ritonavir for symptomatic COVID-19 patients targeting elderly patients would be highly cost-effective and would substantially reduce the demand for hospital admission to below the capacity of the health system if targeted to all adult patients instead of standard care.

Predicted and Observed Incidence of Thromboembolic Events among Koreans Vaccinated with ChAdOx1 nCoV-19 Vaccine.

We used the nationwide claims database to calculate the incidence of thrombotic events and predict their overall 2-week incidence. From 2006 to 2020, the incidence of deep vein thrombosis (DVT), pulmonary embolism (PE), and disseminated intravascular coagulation (DIC) tended to increase. Unlike intracranial venous thrombosis (ICVT) and intracranial thrombophlebitis (ICTP), which showed no age difference, other venous embolism, and thrombosis (OVET), DIC, DVT, and PE were significantly more common in over 65 years. The overall 2-week incidence of ICVT was 0.21/1,000,000 (95% confidence interval [CI], 0.11-0.32). ICTP, OVET, DIC, DVT and PE were expected to occur in 0.08 (95% CI, 0.02-0.14), 7.66 (95% CI, 6.08-9.23), 5.95 (95% CI, 4.88-7.03), 13.28 (95% CI, 11.92-14.64), 14.09 (95% CI, 12.80-15.37) per 1,000,000, respectively. To date, of 8,548,231 patients vaccinated with ChAdOx1 nCoV-19 in Korea, two had confirmed thrombosis with thrombocytopenia syndrome within 2 weeks. The observed incidence of ICVT after vaccination was 0.23/1,000,000.

Effect of meteorological factors and air pollutants on fractures: a nationwide population-based ecological study.

OBJECTIVE: To determine the association of meteorological factors and air pollutants (MFAPs) with fracture and to estimate the effect size/time lag. DESIGN: This is a nationwide population-based ecological study from 2008 to 2017. SETTING: Eight large metropolitan areas in Korea. PARTICIPANTS: Of 8 093 820 patients with fractures reported in the Korea National Health Insurance database, 2 129 955 were analysed after the data set containing patient data (age, sex and site of fractures) were merged with MFAPs. Data on meteorological factors were obtained from the National Climate Data Center of the Korea Meteorological Administration. Additionally, data on air pollutants (atmospheric particulate matter ≤2.5 µm in diameter (PM2.5), PM10, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide) were obtained from the Air Korea database. PRIMARY AND SECONDARY OUTCOME MEASURES: We hypothesised that there would be an association between MFAPs and the incidence of fracture. A generalised additive model was used while factoring in the non-linear relationship between MFAPs and fractures as well as a time lag ≤7 days. Multivariate analysis was performed. Backward elimination with an Akaike information criterion was used to fit the multivariate model. RESULTS: Overall, in eight urban areas, 2 129 955 patients with fractures were finally analysed. These included 370 344, 187 370, 173 100, 140 358, 246 775, 6501, 228 346, 57 183 and 719 978 patients with hip, knee, shoulder, elbow, wrist, hand, ankle, foot and spine fractures, respectively. Various MFAPs (average temperature, daily rain, wind speed, daily snow and PM2.5) showed significant association with fractures, with positive correlations at time lags 7, 5-7, 5-7, 3-7 and 6-7 days, respectively. CONCLUSIONS: Various MFAPs could affect the occurrence of fractures. The average temperature, daily rain, wind speed, daily snow and PM2.5 were most closely associated with fracture. Thus, improved public awareness on these MFAPs is required for clinical prevention and management of fractures.

Estimating Baseline Incidence of Conditions Potentially Associated with Vaccine Adverse Events: a Call for Surveillance System Using the Korean National Health Insurance Claims Data.

BACKGROUND: Vaccines against coronavirus disease 2019 (COVID-19) are raising concerns about vaccine safety, particularly in the context of large-scale immunization. To address public concerns, we measured the baseline incidence rates of major conditions potentially related to vaccine-related adverse events (VAEs). We aimed to provide a basis for evaluating VAEs and verifying causality. METHODS: Conditions of interest were selected from the US Vaccine Adverse Event Reporting System Table of Reportable Events and a recent report from a European consortium on vaccine surveillance. We used the National Health Insurance Service database in Korea to identify the monthly numbers of cases with these conditions. Data from January 2006 to June 2020 were included. Prediction models were constructed from the observed incidences using an autoregressive integrated moving average. We predicted the incidences of the conditions and their respective 95% confidence intervals (CIs) for January through December 2021. In addition, subgroup analysis for the expected vaccination population was conducted. RESULTS: Mean values (95% CIs) of the predicted monthly incidence of vasovagal syncope, anaphylaxis, brachial neuritis, acute disseminated encephalomyelitis, Bell's palsy, Guillain-Barré syndrome, encephalopathy, optic neuritis, transverse myelitis, immune thrombocytopenic purpura, and systemic lupus erythematosus in 2021 were 23.89 (19.81-27.98), 4.72 (3.83-5.61), 57.62 (51.37-63.88), 0.03 (0.01-0.04), 8.58 (7.90-9.26), 0.26 (0.18-0.34), 2.13 (1.42-2.83), 1.65 (1.17-2.13), 0.19 (0.14-0.25), 0.75 (0.61-0.90), and 3.40 (2.79-4.01) cases per 100,000 respectively. The majority of the conditions showed an increasing trend with seasonal variations in their incidences. CONCLUSION: We measured the incidence of a total of 11 conditions that could potentially be associated with VAEs to predict the monthly incidence in 2021. In Korea, conditions that could potentially be related to VAEs occur on a regular basis, and an increasing trend is observed with seasonality.

Overweight and Obesity are Risk Factors for Coronavirus Disease 2019: A Propensity Score-Matched Case-Control Study.

Although obesity is a risk factor for infection, whether it has the same effect on coronavirus disease 2019 (COVID-19) need confirming. We conducted a retrospective propensity score matched case-control study to examine the association between obesity and COVID-19. This study included data from the Nationwide COVID-19 Registry and the Biennial Health Checkup database, until May 30, 2020. We identified 2,231 patients with confirmed COVID-19 and 10-fold-matched negative test controls. Overweight (body mass index [BMI] 23 to 24.9 kg/m2; adjusted odds ratio [aOR], 1.16; 95% confidence interval [CI], 1.1.03 to 1.30) and class 1 obesity (BMI 25 to 29.9 kg/m2; aOR, 1.27; 95% CI, 1.14 to 1.42) had significantly increased COVID-19 risk, while classes 2 and 3 obesity (BMI ≥30 kg/m2) showed similar but non-significant trend. Females and those <50 years had more robust association pattern. Overweight and obesity are possible risk factors of COVID-19.

Burden of dental caries and periodontal disease in South Korea: An analysis using the national health insurance claims database.

OBJECTIVES: It is essential to measure and monitor the burden of dental caries and periodontal disease (PD) in Korea's ageing population due to their potential impact on morbidity, quality of life and economic condition. This study aimed to quantify the size of burden of dental caries and PD using the disability-adjusted life years (DALYs), and their trends. METHODS: DALYs were estimated using incidence-based approaches to calculate the burden of dental caries and PD from 2013 to 2015 in Korea. Incidence and prevalence were estimated using medical claim data by specific algorithms. Additionally, sensitivity analysis was conducted to investigate possible weakness in the study methodology. To conduct the sensitivity analysis, we modified the algorithms to estimate prevalence and incidence. RESULTS: The burden of dental caries and PD increased by 39.2% and 57.0%, respectively, between 2013 and 2015. In 2015, dental caries and PD ranked 11th and 25th, respectively, in terms of the leading causes of DALYs. The burden of dental caries was the most substantial in children aged 0-9 years, while that of PD was the most substantial among those in their ages of 40 and 50 (per 100 000 population). After sensitivity analysis with a modified disease algorithm, the magnitude of disease burden changed considerably. CONCLUSIONS: Dental caries and PD constitute substantial burdens in South Korea. Despite the known limitations, medical claims data can be a powerful resource for conducting timely and cost-effective measurements of oral health. In countries, where universal dental schemes are available, there is need to estimate the burden of oral disease using claims data, for methodical advances in the research field.

Burden of Disease in Coastal Areas of South Korea: An Assessment Using Health Insurance Claim Data.

BACKGROUND: While measuring and monitoring disease morbidity, it is essential to focus on regions experiencing inequitable health outcomes, especially coastal populations. However, no research investigating population health outcomes in coastal areas has been conducted. Therefore, we aimed to investigate the burden of disease morbidity in coastal areas of South Korea. METHODS: Using an administrative division map and the ArcGIS, we identified and included 496 coastal districts. In this observational study, years lived with disability (YLDs) were estimated using incidence-based approaches to calculate the burden of disease in 2015. Incidence and prevalence cases were collected using National Health Insurance Service (NHIS) medical claim data using a specialized algorithm. RESULTS: Age-standardized years lived with disability (ASYLDs) in the coastal areas were 24,398 per 100,000 population, which is greater than the 22,613 YLDs observed nationwide. In coastal areas, the burden of disease morbidity was higher in females than in males. Diabetes mellitus was the leading specific disease of total YLDs per 100,000 population, followed by low back pain, chronic obstructive pulmonary disease, osteoarthritis, and ischemic stroke. CONCLUSION: In this study, the coastal areas of South Korea carry a higher burden than the national population. Additionally, chronic diseases compose the majority of the health burden in coastal areas. Despite the limitation of data, YLD was the best tool available for evaluating the health outcomes in specific areas, and has the advantage of simplicity and timely analysis.

Complementing conventional infectious disease surveillance with national health insurance claims data in the Republic of Korea.

Surveillance remains an important tool for timely outbreak detection and response. Many countries, including Korea, have established national infectious disease surveillance systems with clinical notification. We aimed to evaluate the National Health Insurance Claims-based Surveillance (NHICS) compared to conventional passive report-based National Infectious Diseases Surveillance (NIDS). Reported to claimed cases ratios (R/C ratio) were evaluated from monthly notifiable disease cases captured by NIDS and NHICS. The relationships between 26 infectious diseases and each surveillance system were analysed using Pearson's correlation analysis and linear regression. There was an overall increase in R/C ratio from 2010-2017 (0.37 to 0.78). In 22 infectious diseases, there was a correlation between NIDS and NHICS. Moreover, claim-based surveillance showed less fluctuating disease incidence rates than report-based surveillance for specific infectious diseases, such as varicella, mumps, and scarlet fever. However, for infectious diseases with episodic outbreaks or low incidence, it was difficult to assess NHICS usefulness. Claim-based surveillance is less affected by limitations of conventional report-based surveillance systems, such as reporting rate. Given delays in claim systems, a claim-based surveillance is expected to be complementary to conventional systems for the detection of various infectious diseases with the advancement of bio-information technology.

Analysis of the Effect of the Elderly's Labor Status on Care Cost at the End of Life.

This study quantitatively analyzes the effects of employment patterns at the time of death of the elderly on the utilization of medical care before death using the cohort data from the National Health Insurance Corporation, controlling mortality to obtain more accurate results. Gender was coded as 0 for males and 1 for females, and average monthly household income was taken as a logarithm to approximate a normal distribution. Care cost at the end of life was defined as the sum of the national health insurance contributions and statutory self-contributions. To measure proximity to death, deceased elderly were divided by the period from last hospital visit to death (except any hospital visit at time of death). We distinguished regular workers, irregular workers, self-employed and employers, unpaid family workers, and unemployed. The data used in this study are sample cohort data from the National Health Insurance Corporation. We examined the relationships between variables through 4 models using negative binomial regression. The effects of employment status on health status were analyzed and adjusted for demographic characteristics, socioeconomic status, and proximity to death. As the dependent variable, medical expenses were taken for 1 year before death. In this study, care costs at end of life were higher when children were economically independent and when the respondent was more educated, had high economic level, and had high average monthly household income. In addition, employment security also had a significant impact on care cost at end of life: Irregular workers spent significantly less than regular workers. The fact that care cost at end of life is differentiated according to employment status suggests that individuals' health exists within a social context, which may also constrain it: There is a risk that people's health status will become determined by socioeconomic status.

Regional Differences in Years of Life Lost in Korea from 1997 to 2015.

BACKGROUND: Reducing the gaps in health inequality at a regional level and improving health equity have been emphasized in Korea, it is essential to accurately measure the burden of disease by region. This study aimed to estimate years of life lost (YLLs) in 17 Si and Do of Korea from 1997 to 2015 and determine the trends of regional differences in health status and disease structure. METHODS: YLL was calculated by subtracting the age at death from the life expectancy. Data on the region, gender, and age-stratified cause-specific death were obtained from the Korean Statistical Information Service of Statistics Korea. RESULTS: Age-standardized YLLs per 100,000 population decreased by year in all regions from 1997 to 2015 by 27.4% (27.5% for men; 27.2% for women). Despite the decline in YLLs, the regions with the highest and lowest YLLs did not change between 1997 and 2015. The diseases showing regional differences were caused by injury, often classified as avoidable mortality. We also confirmed that YLLs were higher in the regions with a higher deprivation index. CONCLUSION: The present study identified that YLLs differed by regions in Korea with specific causes. The findings of this study can be used by decision-makers to prioritize the reduction of regional gaps in premature deaths.