Vaccine Effectiveness Against Severe Acute Respiratory Syndrome Coronavirus 2 Reinfection by Type and Frequency of Vaccine: A Community-Based Case-Control Study.

BACKGROUND: Although guidelines recommend vaccination for individuals who have recovered from the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection to prevent reinfection, comprehensive evaluation studies are limited. We aimed to evaluate vaccine effectiveness against SARS-CoV-2 reinfection according to the primary vaccination status, booster vaccination status, and vaccination methods used. METHODS: This population-based case-control study enrolled all SARS-CoV-2-infected patients in Seoul between January 2020 and February 2022. Individuals were categorized into case (reinfection) and control (no reinfection) groups. Data were analyzed using conditional logistic regression after adjusting for underlying comorbidities using multiple regression. RESULTS: The case group included 7,678 participants (average age: 32.26 years). In all vaccinated individuals, patients who received the first and second booster doses showed reduced reinfection rates compared with individuals who received basic vaccination (odds ratio [OR] = 0.605, P < 0.001 and OR = 0.002, P < 0.001). Patients who received BNT162b2 or mRNA-1273, NVX-CoV2373 and heterologous vaccination showed reduced reinfection rates compared with unvaccinated individuals (OR = 0.546, P < 0.001; OR = 0.356, P < 0.001; and OR = 0.472, P < 0.001). However, the ChAdOx1-S or Ad26.COV2.S vaccination group showed a higher reinfection rate than the BNT162b2 or mRNA-1273 vaccination group (OR = 4.419, P < 0.001). CONCLUSION: In SARS-CoV-2-infected individuals, completion of the basic vaccination series showed significant protection against reinfection compared with no vaccination. If the first or second booster vaccination was received, the protective effect against reinfection was higher than that of basic vaccination; when vaccinated with BNT162b2 or mRNA-1273 only or heterologous vaccination, the protective effect was higher than that of ChAdOx1-S or Ad26.COV2.S vaccination only.

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.

Epidemiology and evaluation of adverse drug reactions in a Korean hospital database for spontaneous reports in the period 2009 to 2018.

OBJECTIVE: To evaluate the epidemiology of adverse drug reactions (ADRs) in the Korean population and to identify their characteristics and factors affecting their severity. MATERIALS AND METHODS: The analysis was based on the ADRs reported to the Seoul National University Hospital between 2009 and 2018. Statistical assessment (SPSS Statistics 25) included frequency analysis and the χ2-test. Risk factors were assessed using logistic regression analysis. Results were considered significant at p < 0.05. RESULTS: A total of 44,122 cases were analyzed of which 24,801 (56.2%) cases concerned females and 19,321 (43.8%) males. A total of 47% of cases involved persons aged between 50 and 79 years. Antineoplastic agents, immunomodulating agents, and systemically administered anti-infective agents accounted for 57.6% of all drugs reported. Gastro-intestinal system disorders accounted for the largest proportion (25.8%) of adverse drug reactions reported. A total of 3,429 (7.8%) ADRs were reported as being in the category severe. Multivariate analysis showed that the risk of an ADR being reported as severe is higher in males than in females (OR = 1.25, 95% CI: 1.16 - 1.35), and higher in those aged 0 - 4 years (OR = 1.74, 95% CI: 1.46 - 2.08), in those aged 5 - 19 years (OR = 1.19, 95% CI: 1.07 - 1.31), and in those aged 65 years and over (OR = 1.26, 95% CI: 1.16 - 1.37), compared to those aged 20 - 64 years. DISCUSSION AND CONCLUSION: From a public health perspective, ADRs are important because they are preventable. Important determinants, such as differences in specific age groups and drug classes, for the occurrence of ADRs and the occurrence of severe ADRs in particular, were identified. These determinants need to be carefully monitored in both private medical practices, clinics and hospitals. This monitoring of specific groups will involve close attention factors associated with gender, age group, and drug classes.

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.

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.

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.

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.

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.

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.

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, 10th Revision 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.

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.

The impact of expanded brucellosis surveillance in beef cattle on human brucellosis in Korea: an interrupted time-series analysis.

BACKGROUND: Korean surveillance program for bovine brucellosis was improved by extending it to beef slaughterhouses and by pre-movement testing of bulls on May 2005 (Intervention 1). The bovine brucellosis surveillance program was further extended to beef cattle farms with more than 10 heads of cattle on June 2006 (Intervention 2). METHODS: To quantify the temporal relationship between bovine and human brucellosis, a time-series analysis was conducted using Korean national notification data reported between January 2004 and December 2014. RESULTS: Our findings indicate that while during the pre-intervention phase (January 2004 to March 2005) there was no significant temporal relationship between the incidences of bovine and human brucellosis, significant temporal relationships were observed after Intervention 1 (June 2005 to June 2006, no lag, ß = 0.57, p = 0.04), and Intervention 2 (July 2006 to June 2007, 1-month lag, ß = 0.65, p = 0.03). Furthermore, significant changes in incidence in human were observed after Intervention 1 (ß = - 0.17 per 10 million-people, p = 0.03) and Intervention 2 (ß = - 0.19 per 10 million-people, p = 0.04). CONCLUSIONS: These findings indicated the changes of a nationwide comprehensive surveillance programme targeting all cattle is required for effective reduction in the human population.

An outbreak of respiratory tract infection due to Respiratory Syncytial Virus-B in a postpartum center.

BACKGROUND: An outbreak of respiratory tract infection due to Respiratory Syncytial Virus (RSV) type B in a postpartum center was reported on February 1, 2017. Investigation was conducted to identify the magnitude, possible source of infection and risk factors for this outbreak on February 2, 2017. METHODS: A retrospective cohort study was conducted. A case was defined as a neonate having respiratory symptoms with or without fever and stayed at the postpartum center between January 1, 2017 and February 3, 2017. Daily records of neonates were reviewed, and all parents who stayed at the postpartum center were interviewed. Virological testing of real-time polymerase chain reaction was conducted for the neonates having respiratory illness, the parents and all staff members in the facility. RESULTS: This outbreak occurred between January 17, 2017 and February 7, 2017 in a postpartum center. Thirty-five (58.3%) neonates among 59 neonates were identified as cases and 12 neonates were confirmed to be RSV-B positive. The longer length of stay in the postpartum center is the only risk factor (Relative Risk = 8.10, 95% Confidence Interval:1.84-35.62, p < 0.01) in this outbreak. Two nursing staffs and eight parents were confirmed as RSV-B positive. CONCLUSIONS: Longer periods of stay in the postpartum center had an increased chance of becoming infected with RSV during this outbreak. Isolation of cases and temporary closure with environmental cleaning were recommended to the postpartum center.

Bibliographical Characteristics of North Korean Medical Journals and Articles.

The aim of our work was to analyze the bibliographical characteristics of 9 North Korean medical journals and articles. All journals show only ten pieces of information, such as publication dates and table of contents, and do not provide submission guidelines and journal policy. Most of the journals were published four times a year. Editorials often share government policy. Research articles are very short and compressed. The journals often publish articles on oriental medicine and medical information useful to the public. In conclusion, the journals were published in their own unique style and format, which are far from the global standard.

Reliability of self-reported questionnaire on occupational radiation practices among diagnostic radiologic technologists.

BACKGROUND: We aimed to assess the reliability of a self-reported questionnaire on occupational radiation practices among radiologic technologists. METHODS: We enrolled 941 participants who had repeatedly completed the questionnaire from the 2012-2013 radiologic technologists' health study in South Korea. We used percentage agreement, kappa statistics, and intraclass correlation coefficient (ICC) to assess the reliability of responses on work practices. RESULTS: Overall agreement for ever-never diagnostic radiation procedures was high (87.5-97.5%), and κ values indicated substantial agreement (0.66-0.86) in all procedures except cephalometric and intraoral radiography. For the information of year of work start and working duration, high agreement was obtained (ICC: 0.99 and 0.98, respectively). However, use of a worn dosimeter and of personal protective equipment showed only moderate to substantial agreement. CONCLUSIONS: Self-reported information on working practices regarding radiation exposure in radiologic technologists was reliable enough for epidemiologic studies. Am. J. Ind. Med. 60:377-385, 2017. © 2017 Wiley Periodicals, Inc.

Association between self-perception period of lower urinary tract symptoms and International Prostate Symptom Score: a propensity score matching study.

BACKGROUND: Most studies focusing on progression of BPH have been limited to the relationship between age and BPH progression, and only few studies have focused on the time duration to start treatment. This study aimed to investigate the association between self-perception period (S-PP) of lower urinary tract symptoms (LUTS) and International Prostate Symptom Score (IPSS). METHODS: This study used data from two large-population surveys: a community-based survey and a university hospital outpatient-based interview survey. Both surveys were conducted in male subjects aged 40 years or older who gave consent to the survey questionnaire and voluntarily expressed their intention to participate. Propensity score matching (PSM) was used to organize the population in both surveys into randomized groups to reduce selection bias. After excluding those who had missing values, 483 subjects were assigned to each group by PSM. RESULTS: The S-PP of LUTS became significantly longer as the severity of LUTS increased. The S-PP was 4.15 years in the mild group, 4.36 years in the moderate group, and 6.23 years in the severe group. These differences were statistically significant. The correlation between S-PP of LUTS and IPSS was measured by partial correlation while controlling for age (correlation coefficient = 0.20, p <0.001). Multiple regression analysis after controlling for age revealed that one-year increase in the S-PP of LUTS significantly (p <0.001) increased IPSS by 0.322 points. CONCLUSIONS: This study clarified the association between S-PP of LUTS and IPSS in a large-scale population. These findings suggest that, from the perspective of public health, S-PP is an important risk factor for LUTS progression.

A cluster of lung injury cases associated with home humidifier use: an epidemiological investigation.

BACKGROUND: In April 2011 a tertiary hospital in Seoul, Korea reported several cases of severe respiratory distress of unknown origin in young adults. METHODS: To find the route of transmission, causative agent and patient risk factors of the outbreak, an investigation of the epidemic was initiated. Clinicopathological conferences led to the suspicion that the cases related to an inhalation injury. An age- and sex-matched case-control study was therefore performed to examine the inhalation exposure of the patients to various agents. RESULTS: Of the 28 confirmed cases, 18 agreed to participate. A total of 121 age- and sex-matched controls with pulmonary, allergic or obstetric disease were selected. All patients and controls completed questionnaires with questions about exposure to various inhalants. The crude ORs for patient exposure to indoor mould, humidifier use, humidifier detergent use and insecticide use were 4.4 (95% CI 1.5 to 13.1), 13.7 (95% CI 1.8 to 106.3), 47.3 (95% CI 6.1 to 369.7) and 3.9 (95% CI 1.3 to 11.7), respectively. However, when considered concurrently, indoor mould and insecticide use lost statistical significance. Moreover, humidifier use was ruled out as the cause because of a lack of biological plausibility and the weak strength of the association. This suggested that humidifier disinfectant was the cause of the outbreak. This information led the Korean government to order the removal of humidifier detergents from the market. In the years following the ban, no additional cases were detected. CONCLUSIONS: Epidemiological evidence strongly suggests that the lung injury outbreak was caused by humidifier detergent use at home.

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.

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.