Risk of Severe COVID-19 and Protective Effectiveness of Vaccination Among Solid Organ Transplant Recipients.

BACKGROUND: Solid organ transplant recipients (SOTRs) are at higher risk for severe infection. However, the risk for severe COVID-19 and vaccine effectiveness among SOTRs remain unclear. METHODS: This retrospective study used a nationwide health care claims database and COVID-19 registry from the Republic of Korea (2020 to 2022). Adult SOTRs diagnosed with COVID-19 were matched with up to 4 non-SOTR COVID-19 patients by propensity score. Severe COVID-19 was defined as treatment with high-flow nasal cannulae, mechanical ventilation, or extracorporeal membrane oxygenation. RESULTS: Among 6783 SOTRs with COVID-19, severe COVID-19 was reported with the highest rate in lung transplant recipients (13.16%), followed by the heart (6.30%), kidney (3.90%), and liver (2.40%). SOTRs had a higher risk of severe COVID-19 compared to non-SOTRs, and lung transplant recipients showed the highest risk (adjusted odds ratio, 18.14; 95% confidence interval [CI], 8.53-38.58). Vaccine effectiveness against severe disease among SOTRs was 47% (95% CI, 18%-65%), 64% (95% CI, 49%-75%), and 64% (95% CI, 29%-81%) for 2, 3, and 4 doses, respectively. CONCLUSIONS: SOTRs are at significantly higher risk for severe COVID-19 compared to non-SOTRs. Vaccination is effective in preventing the progression to severe COVID-19. Efforts should be made to improve vaccine uptake among SOTRs, while additional protective measures should be developed.

Prevalence and Burden of Human Adenovirus-Associated Acute Respiratory Illness in the Republic of Korea Military, 2013 to 2022.

BACKGROUND: Human adenovirus (HAdV) is a common cause of acute respiratory disease (ARD) and has raised significant concerns within the Korean military. Here, we conducted a comprehensive epidemiological analysis of HAdV-associated ARD by evaluating its prevalence, clinical outcomes, and prognosis. METHODS: We reviewed data from multiple sources, including the New Defense Medical Information System, Defense Medical Statistical Information System, Ministry of National Defense, Army Headquarters, Navy Headquarters, Air Force Headquarters, and Armed Forces Medical Command. We analyzed data of patients who underwent polymerase chain reaction (PCR) testing for respiratory viruses between January 2013 and July 2022 in all 14 Korean military hospitals. The analysis included the PCR test results, demographic characteristics, health care utilization, and prognosis including types of treatments received, incidence of pneumonia, and mortality. RESULTS: Among the 23,830 individuals who underwent PCR testing at Korean military hospitals, 44.78% (10,670 cases) tested positive for respiratory viruses. Across all military types and ranks, HAdV was the most prevalent virus, with a total of 8,580 patients diagnosed, among HAdV, influenza virus, human metapneumovirus, human parainfluenza virus, and human respiratory syncytial virus. HAdV-infected patients exhibited higher rates of healthcare use compared to non-HAdV-infected patients, including a greater number of emergency visits (1.04 vs. 1.02) and outpatient visits (1.31 vs. 1.27), longer hospitalizations (8.14 days vs. 6.84 days), and extended stays in the intensive care unit (5.21 days vs. 3.38 days). Furthermore, HAdV-infected patients had a higher proportion of pneumonia cases (65.79% vs. 48.33%) and greater likelihood of receiving advanced treatments such as high flow nasal cannula or continuous renal replacement therapy. CONCLUSION: Our findings indicate that HAdV posed a significant public health concern within the Korean military prior to the coronavirus disease 2019 (COVID-19) pandemic. Given the potential for a resurgence of outbreaks in the post-COVID-19 era, proactive measures, such as education, environmental improvements, and the development of HAdV vaccines, are crucial for effectively preventing future outbreaks.

Lack of association between fluoroquinolone and aortic aneurysm or dissection.

BACKGROUND AND AIMS: An increased risk of aortic aneurysm and aortic dissection (AA/AD) has been reported with fluoroquinolone (FQ) use. However, recent studies suggested confounding factors by indication. This study aimed to investigate the risk of AA/AD associated with FQ use. METHODS: This nationwide population-based study included adults aged ≥20 years who received a prescription of oral FQ or third-generation cephalosporins (3GC) during outpatient visits from 2005 to 2016. Data source was the National Health Insurance Service reimbursement database. The primary outcome was hospitalization or in-hospital death with a primary diagnosis of AA/AD. A self-controlled case series (SCCS) and Cox proportional hazards model were used. Self-controlled case series compared the incidence of the primary outcome in the risk period vs. the control periods. RESULTS: A total of 954 308 patients (777 109 with FQ and 177 199 with 3GC use) were included. The incidence rate ratios for AA/AD between the risk period and the pre-risk period were higher in the 3GC group [11.000; 95% confidence interval (CI) 1.420-85.200] compared to the FQ group (2.000; 95% CI 0.970-4.124). The overall incidence of AA/AD among the patients who received FQ and 3GC was 5.40 and 8.47 per 100 000 person-years. There was no significant difference in the risk between the two groups (adjusted hazard ratio 0.752; 95% CI 0.515-1.100) in the inverse probability of treatment-weighted Cox proportional hazards model. Subgroup and sensitivity analysis showed consistent results. CONCLUSIONS: There was no significant difference in the risk of AA/AD in patients who were administered oral FQ compared to those administered 3GC. The study findings suggest that the use of FQ should not be deterred when clinically indicated.

Herpes Zoster Reactivation After mRNA and Adenovirus-Vectored Coronavirus Disease 2019 Vaccination: Analysis of National Health Insurance Database.

BACKGROUND: Our study aimed to determine the risk of herpes zoster reactivation and coronavirus disease 2019 (COVID-19) vaccination (mRNA vaccine [BNT162b2] and adenovirus-vectored vaccine [ChAdOx1 nCoV-19]). METHODS: This retrospective study analyzed herpes zoster cases diagnosed between 26 February 2021 and 30 June 2021 and registered in the National Health Insurance Service database. A matched case-control study with a 1:3 matching ratio and a propensity score matching (PSM) study with a 1:1 ratio of vaccinated and unvaccinated individuals were performed. RESULTS: In the matched case control analysis, BNT162b2 was associated with an increased risk of herpes zoster reactivation (first dose adjusted odds ratio [aOR], 1.11; 95% confidence interval [CI], 1.06-1.15; second dose aOR, 1.17; 95% CI, 1.12-1.23). PSM analysis revealed a statistically significant increase in risk within 18 days following any vaccination (adjusted hazard ratio [aHR], 1.09; 95% CI, 1.02-1.16). BNT162b2 was associated with an increased risk at 18 days postvaccination (aHR, 1.65; 95% CI, 1.35-2.02) and second dose (aHR, 1.10; 95% CI, 1.02-1.19). However, the risk did not increase in both analyses of ChAdOx1 vaccination. CONCLUSIONS: mRNA COVID-19 vaccination possibly increases the risk of herpes zoster reactivation, and thus close follow-up for herpes zoster reactivation is required.

Risk of breakthrough SARS-CoV-2 infection and clinical outcomes among vaccinated patients with type 2 diabetes.

AIM: To explore the risk of breakthrough infection among patients with type 2 diabetes (T2D) and risk of severe clinical outcomes after SARS-CoV-2 infection according to vaccination status. MATERIALS AND METHODS: We conducted a population-based cohort study using South Korea's linked database of nationwide COVID-19 registry and claims data between 2018 and 2021. Hazard ratios (HRs) and 95% confidence intervals (CIs) for breakthrough infections were measured in 1:1 propensity-score (PS)-matched fully vaccinated patients with versus without T2D (full-vaccination cohort), and HRs for all-cause mortality, intensive care unit (ICU) admission/mechanical ventilation (MV) use, and hospitalizations after SARS-CoV-2 infection were measured in 1:1 PS-matched T2D patients with versus without full-vaccination (T2D cohort). RESULTS: After 1:1 PS matching, 2 109 970 patients with and without T2D were identified (age 63.5 years; 50.9% male). Patients with T2D showed an increased risk of breakthrough infections compared to those without T2D (HR 1.10, 95% CI 1.06-1.14). The increased risk of breakthrough infections was more notable among T2D patients receiving insulin treatment. However, the risk of severe COVID-19 outcomes was lower in fully vaccinated T2D patients compared with unvaccinated T2D patients (all-cause mortality: HR 0.54, 95% CI 0.43-0.67; ICU admission/MV use: HR 0.31, 95% CI 0.23-0.41; hospitalization: HR 0.73, 95% CI 0.68-0.78). CONCLUSIONS: While patients with T2D remain a vulnerable population to SARS-CoV-2 infection even after full-vaccination, full-vaccination was associated with a lower risk of adverse clinical outcomes after SARS-CoV-2 infection. These findings support the guidelines recommending patients with T2D as a priority vaccination group.

A Model-Based Cost-Effectiveness Analysis of Long-Acting Monoclonal Antibody (Tixagevimab and Cilgavimab: Evusheld) Preventive Treatment for High-Risk Populations Against SARS-CoV-2 in Korea.

BACKGROUND: Tixagevimab and cilgavimab (Evusheld) administration is a recommended strategy for unvaccinated patients with immunocompromised conditions and severe allergic reaction conditions to protect high-risk individuals and control the coronavirus disease 2019 (COVID-19) epidemic. We estimated the cost-effectiveness of Evusheld in key risk populations: 1) immunocompromised (vaccinated/unvaccinated), 2) severe allergic reaction, and 3) unvaccinated elderly high-risk groups. METHODS: Based on the estimated target risk group population, we used a model of COVID-19 transmission to estimate the size of the risk group population for whom Evusheld treatment may help prevent symptomatic COVID-19 (and deaths) in 2022. We projected Evusheld intervention costs, quality-adjusted life year (QALY) lost, cost averted and QALY gained by reduced COVID-19 incidence, and incremental cost-effectiveness (cost per QALY gained) in each modeled population from the healthcare system perspective. RESULTS: Our study demonstrated that Evusheld treatment for COVID-19 infection in South Korea is highly cost-effective for unvaccinated risk groups ($18,959 per QALY gained for immunocompromised and $23,978 per QALY gained for high-risk elderly groups) and moderately cost-effective among individuals who are vaccinated immunocompromised ($46,494 per QALY gained), or have severe allergic reactions ($45,996 per QALY gained). Evusheld's cost-effectiveness may be subject to risk-group-specific COVID-19 disease progression and Evusheld efficacy and cost, which may change in future epidemic scenarios. CONCLUSION: As the COVID-19 variants and risk group-specific durable efficacy, toxicity (and/or resistance) and optimal dosing of Evusheld remain uncertain, better empirical estimates to inform these values in different epidemiological contexts are needed. These results may help decision-makers prioritize resources toward more equitable and effective COVID-19 control efforts.

Effective Vaccination and Education Strategies for Emerging Infectious Diseases Such as COVID-19.

Social isolation and control owing to coronavirus disease 2019 (COVID-19) are easing; however, concerns regarding new infectious diseases have not disappeared. Given epidemic experiences such as severe acute respiratory syndrome (SARS), the influenza pandemic, Middle East respiratory syndrome (MERS), and COVID-19, it is necessary to prepare for the outbreak of new infectious diseases and situations in which large-scale vaccinations are required. Although the development of vaccines against COVID-19 has contributed greatly to overcoming the pandemic, concerning vaccine side effects from the general public, including medical personnel, and decreased confidence in vaccine efficacy and side effects, present many challenges in promoting and educating vaccinations for new infectious diseases in the future. In addition to plans to develop vaccines for the outbreak of new infectious diseases, education and promotion plans are necessary to administer the latest developments of vaccines to the general public. Moreover, efforts are needed to secure the necessity, legitimacy, and evidence for rapid vaccination on a large scale at the national level. It is also necessary to carefully prepare scientific bases and explanatory statements so that the general public can easily understand them. This study aimed to establish vaccine strategies and vaccination education plans for new infectious diseases that may occur in the future. Many ways to promote vaccination to the general public and healthcare workers should be prepared to ensure that the latest vaccines against new infectious diseases are administered safely. Thus, education and promotion of vaccine efficacy and safety based on specific data from clinical studies are necessary.

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.

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.

COVID-19 Vaccination Status Among Korean Pediatric Population With Comorbidities.

The pediatric population with comorbidities is a high-risk group for severe coronavirus disease 2019 (COVID-19). As of January 2023, the COVID-19 vaccination rate for at least two doses among Korean children 5-11 years is low at 1.1%. We summarized the COVID-19 vaccination status for the pediatric population (5-17 years) with comorbidities through July 2022 using the National Health Insurance Service database. Pediatric patients with comorbidities had higher vaccination rates than the general pediatric population (2.4% vs. 1.1% in 5-11-year-olds [P < 0.001], 76.5% vs. 66.1% in 12-17-year-olds [P < 0.001]). However, there were substantial differences according to comorbidity category, and the 2-dose vaccination rate was lowest among children with immunodeficiency in all age groups (1.1% in 5-11-year-olds, 51.2% in 12-17-year-olds). The COVID-19 vaccination rate among Korean children has remained stagnant at a low proportion despite ongoing outreach. Thus, more proactive strategies are needed alongside continuous surveillance.

Predictors of COVID-19 Vaccine Hesitancy Among Parents of Children Aged 5-11 Years in Korea.

This was a cross-sectional study using the data collected from a nationwide survey between November and December 2022 to explore factors associated with hesitancy towards coronavirus disease 2019 (COVID-19) vaccination for children. Among 3,011 participants with child aged 5-11 years, 82.5% demonstrated hesitancy towards vaccinating their child. This was more common among mothers (odds ratio 1.84 [95% confidence interval 1.46-2.31]), those residing outside metropolitan area (urban: 2.46 [1.89-3.20]; rural: 2.87 [2.09-3.93]) or with history of COVID-19 diagnosis (2.22 [1.78-2.76]). Parents were also hesitant if their child recently had COVID-19 (3.41 [2.67-4.37]). Conversely, they were less likely to be hesitant if they had three or more children (0.66 [0.46-0.94]) or if their child has underlying medical condition(s) (0.54 [0.41-0.71]). Our findings highlight high prevalence of parental hesitancy towards COVID-19 vaccination for children, and call for targeted outreach efforts from the stakeholders to facilitate the vaccine uptake in this pediatric population.

A Nationwide Survey of mRNA COVID-19 Vaccinee's Experiences on Adverse Events and Its Associated Factors.

BACKGROUND: Although coronavirus disease 2019 (COVID-19) vaccines have been distributed worldwide under emergency use authorization, the real-world safety profiles of mRNA vaccines still need to be clearly defined. We aimed to identify the overall incidence and factors associated with adverse events (AEs) following mRNA COVID-19 vaccination. METHODS: We conducted web-based survey from December 2 to 10 in 2021 with a 2,849 nationwide sampled panel. Study participants were individuals who had elapsed at least two-weeks after completing two dosing schedules of COVID-19 vaccination aged between 18-49 years. We weighted the participants to represent the Korean population. The outcome was the overall incidence of AEs following mRNA COVID-19 vaccination and associated factors. We estimated the weighted odds ratios (ORs) using multivariable logistic regression models to identify the factors associated with AEs. RESULTS: Of the 2,849 participants (median [interquartile range] age, 35 [27-42] years; 51.6% male), 90.8% (n = 2,582) for the first dose and 88.7% (n = 2,849) for the second dose reported AEs, and 3.3% and 4.3% reported severe AEs, respectively. Occurrence of AEs was more prevalent in mRNA-1273 (OR, 2.06; 95% confidence interval [CI], 1.59-2.67 vs. BNT162b2), female sex (1.88; 1.52-2.32), and those with dermatologic diseases (2.51; 1.32-4.77). History of serious allergic reactions (1.96; 1.06-3.64) and anticoagulant medication use (4.72; 1.92-11.6) were associated with severe AEs. CONCLUSION: Approximately 90% of participants reported AEs following mRNA COVID-19 vaccination. Substantial factors, including vaccine type (mRNA-1273), female sex, and dermatologic diseases were associated with AEs. Our findings could aid policymakers in establishing vaccination strategies tailored to those potentially susceptible to AEs.

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.

Antibiotic Prescription in Patients With Coronavirus Disease 2019: Analysis of National Health Insurance System Data in the Republic of Korea.

BACKGROUND: Although coronavirus disease 2019 (COVID-19) is a viral infection, antibiotics are often prescribed due to concerns about accompanying bacterial infection. Therefore, we aimed to analyze the number of patients with COVID-19 who received antibiotic prescriptions, as well as factors that influenced antibiotics prescription, using the National Health Insurance System database. METHODS: We retrospectively reviewed claims data for adults aged ≥ 19 years hospitalized for COVID-19 from December 1, 2019 to December 31, 2020. According to the National Institutes of Health guidelines for severity classification, we calculated the proportion of patients who received antibiotics and the number of days of therapy per 1,000 patient-days. Factors contributing to antibiotic use were determined using linear regression analysis. In addition, antibiotic prescription data for patients with influenza hospitalized from 2018 to 2021 were compared with those for patients with COVID-19, using an integrated database from Korea Disease Control and Prevention Agency-COVID19-National Health Insurance Service cohort (K-COV-N cohort), which was partially adjusted and obtained from October 2020 to December 2021. RESULTS: Of the 55,228 patients, 46.6% were males, 55.9% were aged ≥ 50 years, and most patients (88.7%) had no underlying diseases. The majority (84.3%; n = 46,576) were classified as having mild-to-moderate illness, with 11.2% (n = 6,168) and 4.5% (n = 2,484) having severe and critical illness, respectively. Antibiotics were prescribed to 27.3% (n = 15,081) of the total study population, and to 73.8%, 87.6%, and 17.9% of patients with severe, critical, and mild-to-moderate illness, respectively. Fluoroquinolones were the most commonly prescribed antibiotics (15.1%; n = 8,348), followed by third-generation cephalosporins (10.4%; n = 5,729) and beta-lactam/beta-lactamase inhibitors (6.9%; n = 3,822). Older age, COVID-19 severity, and underlying medical conditions contributed significantly to antibiotic prescription requirement. The antibiotic use rate was higher in the influenza group (57.1%) than in the total COVID-19 patient group (21.2%), and higher in severe-to-critical COVID-19 cases (66.6%) than in influenza cases. CONCLUSION: Although most patients with COVID-19 had mild to moderate illness, more than a quarter were prescribed antibiotics. Judicious use of antibiotics is necessary for patients with COVID-19, considering the severity of disease and risk of bacterial co-infection.

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.

The Possible Impact of Nationwide Vaccination on Outcomes of the COVID-19 Epidemic in North Korea: A Modelling Study.

BACKGROUND: The Democratic People's Republic of Korea (North Korea) had successfully suppressed the coronavirus disease 2019 (COVID-19) epidemic via border closures. However, a rapid surge in incidence was reported due to the spread of the omicron variant (B.1.1.529), leading to a national emergency declaration in May 2022. Moreover, with the lack of vaccine accessibility and medical facilities, it is unclear how the disease burden may be exacerbated. Despite the limited epidemiological data, we aimed to project the COVID-19 transmissions in North Korea and quantify the potential impact of nationwide vaccination, comparing epidemiological outcomes via scenario analysis. METHODS: A discrete-time deterministic compartmental model was used. The parameters were calibrated using empirical data. Numerical simulations incorporated nationwide COVID-19 vaccination into the proposed model with various asymptomatic proportions. RESULTS: Our model suggested that the stringent public health and social measures (PHSMs) reduced the severe acute respiratory syndrome coronavirus 2 transmissibility by more than 80% in North Korea. Projections that explicitly incorporated vaccination indicated that nationwide vaccination would be necessary to suppress a huge resurgence in both COVID-19 cases and hospitalizations after the stringent PHSMs are eased. Moreover, vaccinating more than 80% of the population with two doses may keep the peak prevalence of hospitalizations below 1,500, averting more than 40,000 hospitalizations across all scenarios. CONCLUSION: Nationwide vaccination would be essential to suppress the prevalence of COVID-19 hospitalizations in North Korea after the stringent PHSMs are lifted, especially in the case of a small asymptomatic proportion.

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.

Relationship Between Appendectomy Incidence and Computed Tomography Scans Based on Korean Nationwide Data, 2003-2017.

BACKGROUND: Advances in medicine and changes in the medical environment can affect the diagnosis and treatment of diseases. The main purpose of the present study was to investigate whether the difference in accessibility to diagnosis and treatment facilities influenced the occurrence of appendectomy in Korea. METHODS: We collected data on 183,531 appendectomy patients between 2003 and 2017 using the National Health Insurance Services claims. Retrospective analysis of relationship between the age-standardized rate (ASR) of appendectomy and clinical variables affecting medical accessibility was performed. Pearson's correlation analyses were used. RESULTS: The incidence of appendectomy decreased from 30,164 cases in 2003 to 7,355 cases in 2017. The rate of computerized tomography (CT) scans for diagnosis of appendicitis increased from 4.73% in 2003 to 86.96% in 2017. The ASR of appendectomy in uncomplicated and complicated appendicitis decreased from 48.71 in 2005 to 13.40 in 2010 and 8.37 in 2005 to 2.96 in 2009, respectively. The ASR of appendectomy was higher in the high-income group. The proportion and ASR of appendectomy in older age group increased steadily with years. The total admission days continued to decrease from 6.02 days in 2003 to 4.96 days in 2017. CONCLUSION: The incidence of appendectomy was seemingly associated with the rate of CT scan. In particular, the incidence of appendectomy in uncomplicated appendicitis was markedly reduced. Through enhanced accessibility to CT scans, accurate diagnosis and treatment of appendicitis can be facilitated.

COVID-19 Vaccination Rates in Patients With Chronic Medical Conditions: A Nationwide Cross-Sectional Study.

As most individuals acquire immunity to severe acute respiratory syndrome coronavirus 2, South Korea declared a return to normalcy a few months ago. However, epidemic waves continue because of endlessly emerging variants and waning immunity. Health authorities are focusing on those at high risk of severe coronavirus disease 2019 to minimize damage to public health and the economy. In this regard, we investigated the vaccination rates in patients with various chronic medical conditions by examining the national health insurance claims data and the national immunization registry. We found that patients with chronic medical conditions, especially those of higher severity, such as malignancy, had vaccination rates approximately 10-20% lower than those of the general population. Public health authorities and healthcare providers should try to vaccinate these patients to avoid preventable morbidity and mortality.

Respiratory Syncytial Virus Outbreak Without Influenza in the Second Year of the Coronavirus Disease 2019 Pandemic: A National Sentinel Surveillance in Korea, 2021-2022 Season.

BACKGROUND: This study aimed to investigate whether respiratory syncytial virus (RSV) and influenza virus (IFV) infections would occur in 2021-2022 as domestic nonpharmaceutical interventions (NPIs) are easing. METHODS: Data were collected from the Korean Influenza and Respiratory Virus Monitoring System database. The weekly positivity rates of respiratory viruses and number of hospitalizations for acute respiratory infections were evaluated (January 2016-2022). The period from February 2020 to January 2022 was considered the NPI period. The autoregressive integrated moving average model and Poisson analysis were used for data analysis. Data from 14 countries/regions that reported positivity rates of RSV and IFV were also investigated. RESULTS: Compared with the pre-NPI period, the positivity and hospitalization rates for IFV infection during 2021-2022 significantly decreased to 0.0% and 1.0%, respectively, at 0.0% and 1.2% of the predicted values, respectively. The RSV infection positivity rate in 2021-2022 was 1.8-fold higher than that in the pre-NPI period at 1.5-fold the predicted value. The hospitalization rate for RSV was 20.0% of that in the pre-NPI period at 17.6% of the predicted value. The re-emergence of RSV and IFV infections during 2020-2021 was observed in 13 and 4 countries, respectively. CONCLUSION: During 2021-2022, endemic transmission of the RSV, but not IFV, was observed in Korea.