Background: The most recent variant of concern, omicron (B.1.1.529), has caused numerous cases worldwide including the Republic of Korea due to its fast transmission and reduced vaccine effectiveness. Methods: A mathematical model considering age-structure, vaccine, antiviral drugs, and influx of the omicron variant was developed. We estimated transmission rates among age groups using maximum likelihood estimation for the age-structured model. The impact of non-pharmaceutical interventions (NPIs; in community and border), quantified by a parameter μ in the force of infection, and vaccination were examined through a multi-faceted analysis. A theory-based endemic equilibrium study was performed to find the manageable number of cases according to omicron- and healthcare-related factors. Results: By fitting the model to the available data, the estimated values of μ ranged from 0.31 to 0.73, representing the intensity of NPIs such as social distancing level. If μ < 0.55 and 300,000 booster shots were administered daily from February 3, 2022, the number of severe cases was forecasted to exceed the severe bed capacity. Moreover, the number of daily cases is reduced as the timing of screening measures is delayed. If screening measure was intensified as early as November 24, 2021 and the number of overseas entrant cases was contained to 1 case per 10 days, simulations showed that the daily incidence by February 3, 2022 could have been reduced by 87%. Furthermore, we found that the incidence number in mid-December 2021 exceeded the theory-driven manageable number of daily cases. Conclusion NPIs, vaccination, and antiviral drugs influence the spread of omicron and number of severe cases in the Republic of Korea. Intensive and early screening measures during the emergence of a new variant is key in controlling the epidemic size. Using the endemic equilibrium of the model, a formula for the manageable daily cases depending on the severity rate and average length of hospital stay was derived so that the number of severe cases does not surpass the severe bed capacity.

The variant B.1.1.7 of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the RNA virus causing the pandemic more than a year worldwide, was reported from United Kingdom (UK) in late December 2020. It was reported that mortality increases by 65% and transmissibility increases by 70%, which may result in an increase of reproduction number to 1.13−1.55 from 0.75−0.85. To analyze the global increasing trend of the variant B.1.1.7, we extracted results of B.1.1.7 from GISAID on May 11 and May 12, 2021, and conducted a doseresponse regression. It took 47 days to reach 20% and 121 days to reach 50% among the sequence submitted from UK. In Korea, cases of B.1.1.7 have increased since the first report of three cases on December 28, 2020. Positive rate of B.1.1.7 in Korea was 21.6% in the week from May 9 to May 15, 2021. Detection rate of the variants is expected to increase further and new variants of SARS-CoV-2 are emerging, so a close monitoring and control would be maintained for months.

The variant B.1.1.7 of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the RNA virus causing the pandemic more than a year worldwide, was reported from United Kingdom (UK) in late December 2020. It was reported that mortality increases by 65% and transmissibility increases by 70%, which may result in an increase of reproduction number to 1.13−1.55 from 0.75−0.85. To analyze the global increasing trend of the variant B.1.1.7, we extracted results of B.1.1.7 from GISAID on May 11 and May 12, 2021, and conducted a doseresponse regression. It took 47 days to reach 20% and 121 days to reach 50% among the sequence submitted from UK. In Korea, cases of B.1.1.7 have increased since the first report of three cases on December 28, 2020. Positive rate of B.1.1.7 in Korea was 21.6% in the week from May 9 to May 15, 2021. Detection rate of the variants is expected to increase further and new variants of SARS-CoV-2 are emerging, so a close monitoring and control would be maintained for months.

Objectives: The incidence of Guillain-Barré syndrome (GBS) changed significantly during the coronavirus disease 2019 (COVID-19) pandemic. Emerging reports suggest that viral vector-based vaccines may be associated with an elevated risk of GBS. Methods: In this nationwide time-series correlation study, we examined the age-specific incidence of GBS from January 2011 to August 2022, as well as data on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccinations and infections from February 2021 to August 2022. We compared the forecasted estimates of age-specific GBS incidence, using the pre-SARS-CoV-2 period as a benchmark, with the actual incidence observed during the post-vaccination period of the pandemic. Furthermore, we assessed the temporal association between GBS, SARS-CoV-2 vaccinations, and COVID-19 for different age groups. Results: In the age group of 60 and older, the rate ratio was significantly elevated during June-August and November 2021. A significant, strong positive association was observed between viral vector-based vaccines and GBS incidence trends in this age group (r=0.52, p=0.022). For the 30 to 59 years age group, the rate ratio was notably high in September 2021. A statistically significant, strong positive association was found between mRNA-based vaccines and GBS incidence in this age group (r=0.61, p=0.006). Conclusion Viral vector-based SARS-CoV-2 vaccines were found to be temporally associated with an increased risk of GBS, particularly in older adults. To minimize age-specific and biological mechanism-specific adverse events, future vaccination campaigns should adopt a more personalized approach, such as recommending homologous mRNA-based SARS-CoV-2 vaccines for older adults to reduce the heightened risk of GBS.

Objectives: Healthcare facilities are high-risk sites for infection. This study analyzed the epidemiological characteristics of a coronavirus disease 2019 (COVID-19) outbreak in a tertiary hospital after COVID-19 vaccination had been introduced in Republic of Korea. Vaccine effectiveness (VE) and shared anti-infection strategies are also assessed. Methods: The risk levels for 4,074 contacts were evaluated. The epidemiological characteristics of confirmed cases were evaluated using the chi-square test. The “1 minus relative risk” method was used to determine VE in preventing infection, progression to severe disease, and death. In the largest affected area (the 8th floor), a separate relative risk analysis was conducted. A multivariate logistic regression analysis (with 95% confidence interval [CIs]) was used to identify transmission risk factors with a significance level <10% via the backward elimination method. Results: In total, 181 cases of COVID-19 were confirmed, with an attack rate of 4.4%. Of those cases, 12.7% progressed to severe disease, and 8.3% died. In the cohort isolation area on the 8th floor, where 79.0% of the confirmed cases occurred, the adjusted odds ratio was 6.55 (95% CI, 2.99–14.33) and 2.19 (95% CI, 1.24–3.88) for caregivers and the unvaccinated group, respectively. VE analysis revealed that 85.8% of the cases that progressed to severe disease and 78.6% of the deaths could be prevented by administering a second vaccine. Conclusion Caregiver training for infection prevention and control is necessary to reduce infection risk. Vaccination is an important intervention to reduce the risk of progression to severe disease and death.

BACKGROUND: Dengue fever is one of the most dominant vector-borne diseases, putting approximately 3.9 billion people at risk worldwide. While it is generally vector-borne, other routes of transmission such as needlestick injury are possible. Laboratory workers can be exposed to dengue virus transcutaneously by needlestick injury. This is the first case, to our knowledge, of dengue virus infection by needlestick injury in a laboratory environment. This paper evaluates the risk and related health concerns of laboratory workers exposed to dengue virus. CASE PRESENTATION: We evaluated a 30-year-old female laboratory worker exposed to the dengue virus by needlestick injury while conducting virus filtering. During admission, she showed symptoms of fever, nausea, myalgia, and a characteristic maculopapular rash with elevated aspartate aminotransferase (AST) of 235 IU/L and alanine aminotransferase (ALT) of 269 IU/L. She had been diagnosed by a positive nonstructural protein 1 (NS1) antigen (Ag) rapid test one day prior to symptom onset along with positive immunoglobulin M (IgM) enzyme-linked immunosorbent assay (ELISA) on the ninth day of symptom onset. Reverse transcription polymerase chain reaction (RT-PCR), also conducted on the ninth day, was negative. After proper symptomatic treatment, she recovered without any sequelae. As a result of thorough epidemiologic investigation, it was determined that she had tried to recap the needle during the virus filtering procedure and a subsequent needlestick injury occurred. CONCLUSIONS: In the context of health promotion of laboratory workers, we suggest that the laboratory biosafety manual be revised and reinforced, and related prevention measures be implemented. Furthermore, health authorities and health care providers in Korea should be fully informed of proper dengue fever management.
Adult ; Alanine Transaminase ; Aspartate Aminotransferases ; Dengue Virus* ; Dengue* ; Enzyme-Linked Immunosorbent Assay ; Exanthema ; Female ; Fever ; Health Personnel ; Health Promotion ; Humans ; Immunoglobulin M ; Korea* ; Myalgia ; Nausea ; Needles ; Needlestick Injuries* ; Polymerase Chain Reaction ; Reverse Transcription

Background: We aimed to analyze the risk factors for sudden death after diagnosis of coronavirus disease 2019 (COVID-19) in South Korea and to provide evidence for informing prevention and control interventions for patients at risk of sudden death. Methods: We included 30,302 COVID-19 related deaths registered in the patient management information system (Central Disease Control Headquarters) between January 1, 2021, and December 15, 2022. We collected their epidemiological data recorded by the reporting city, province, or country. We performed multivariate logistic regression analysis to identify risk factors for sudden death after diagnosis of COVID-19. Results: Among the 30,302 deaths, there were 7,258 (24.0%) and 23,044 (76.0%) sudden and non-sudden deaths, respectively. Sudden death means a person who died within 2 days of diagnosis and who did not receive inpatient treatment. Underlying condition, vaccination status, and place of death were significantly associated with the survival period in all age groups. Moreover, region, sex, and prescription were significantly associated with the survival period only in certain age groups. However, reinfection was not significantly associated with the survival period in any age group. Conclusion To our knowledge, this is the first study on the risk factors for sudden death after a diagnosis of COVID-19, which included age, underlying condition, vaccination status, and place of death. Additionally, individuals aged < 60 years without an underlying condition were at high risk for sudden death. However, this group has relatively low interest in health, as can be seen from the high non-vaccination rate (16.1% of the general population vs. 61.6% of the corresponding group). Therefore, there is a possibility for the presence of an uncontrolled underlying disease in this population. In addition, many sudden deaths occurred due to delayed hospital visits to continue economic activities even after the onset of COVID-19 symptoms (7 days overall vs. 10 days average for the group). In conclusion, ‘continued interest in health’ is a key factor in avoiding sudden death in the economically active group (under 60 years of age).

Objectives: This study aimed to classify coronavirus disease 2019 (COVID-19)-related deaths according to whether COVID-19 was listed as the cause of death, and to investigate thedifferences in demographic characteristics and risk factors for COVID-19 death classifications. Methods: A total of 5,625 deaths in South Korea among patients with confirmed COVID-19 from January 20, 2020 to December 31, 2021 were selected. Excluding false reports and unnatural deaths, 5,597 deaths were analyzed. Based on death report data, deaths were classified according to whether the cause of death was listed as COVID-19 (CD) or not (NCD). The epidemiological characteristics and causes of deaths were investigated using descriptive, univariate, and multivariate statistical analyses. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to analyze the risk factors. Results: The case fatality ratio was 0.89% and increased with age. Additionally, 96.4% of the subjects had an underlying disease, and 53.4% died in winter. The proportion of NCDs was 9.3%, of whom 19.1% died at home and 39.0% were confirmed to have COVID-19 after death. Malignant neoplasms (102/416 vs. 637/4,442; OR, 1.71; 95% CI, 1.36−2.16; p < 0.001) were significantly associated with NCD. Conclusion This is the first study to analyze risk factors by cause of death using COVID-19death report data in South Korea. These results are expected to be used as evidence forestablishing a death monitoring system that can collect timely information in a new infectiousdisease pandemic.

Background: This retrospective observational matched cohort study assessed the differences in critical infections caused by severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) during the omicron-predominant period of the coronavirus disease 2019 (COVID-19) pandemic. We evaluated the vaccine effectiveness of bivalent mRNA vaccine compared to unvaccinated individuals. Methods: We collected COVID-19 case data from the Korean COVID-19 vaccine effectiveness cohort. We calculated the probability of critical COVID-19 cases by comparing the vaccinated and unvaccinated groups. Results: The risk of being critically infected due to SAR-CoV-2 infection was 5.96 times higher (95% confidence interval, 5.63–6.38) among older individuals who were unvaccinated compared to those who received the bivalent COVID-19 vaccine. Conclusion Our findings indicate that the bivalent vaccine reduces the disease burden of the SARS-CoV-2 omicron variant, particularly among the older population. Further studies are warranted to determine the effectiveness of booster doses of vaccines for SARS-CoV-2 infection.

Background: This retrospective observational matched cohort study assessed the differences in critical infections caused by severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) during the omicron-predominant period of the coronavirus disease 2019 (COVID-19) pandemic. We evaluated the vaccine effectiveness of bivalent mRNA vaccine compared to unvaccinated individuals. Methods: We collected COVID-19 case data from the Korean COVID-19 vaccine effectiveness cohort. We calculated the probability of critical COVID-19 cases by comparing the vaccinated and unvaccinated groups. Results: The risk of being critically infected due to SAR-CoV-2 infection was 5.96 times higher (95% confidence interval, 5.63–6.38) among older individuals who were unvaccinated compared to those who received the bivalent COVID-19 vaccine. Conclusion Our findings indicate that the bivalent vaccine reduces the disease burden of the SARS-CoV-2 omicron variant, particularly among the older population. Further studies are warranted to determine the effectiveness of booster doses of vaccines for SARS-CoV-2 infection.