Age-specific Risk of SARS-CoV-2 Reinfection During Omicron Outbreaks, South Korea.

We assessed the risk of reinfection among all residents in South Korea who tested positive for coronavirus disease 2019 from January to August 2022. Children 5-11 years [adjusted hazard ratio (aHR) = 2.20], and 12-17 years old (aHR = 2.00), were at higher risk; whereas 3-dose vaccination (aHR = 0.20) lowered the risk of reinfection.

Effectiveness of Heterologous COVID-19 Vaccine Booster in Korean Elderly Population, 2022.

We conducted a cohort study to assess vaccine effectiveness (VE) of coronavirus disease 2019 vaccine combinations on severe acute respiratory syndrome coronavirus 2 critical infection and death among elderly population in Korea. From January to August 2022, VE against death for 4 doses mRNA recipients was 96.1%, whereas 1-dose viral vector + 3-dose mRNA recipients had VE of 90.8%.

Vaccine Effectiveness Against Severe Disease and Death for Patients With COVID-19 During the Delta-Dominant and Omicron-Emerging Periods: A K-COVE Study.

National cohort data collected during the coronavirus disease 2019 (COVID-19) delta and omicron periods in Korea revealed a lower risk of severe infection in recipients of three doses of the COVID-19 vaccine (adjusted odds ratio [aOR], 0.05-0.08). The risk of death was reduced during the omicron period compared to the delta period (aOR, 0.75; 95% confidence interval, 0.67-0.84).

Effectiveness of A Fourth Dose of COVID-19 mRNA Vaccine in the Elderly Population During the Omicron BA.2 and BA.5 Circulation: A Nationwide Cohort Study in Korea (K-COVE).

We estimate the effectiveness of a fourth dose booster of coronavirus disease 2019 mRNA vaccine in individuals aged ≥60 years during Omicron BA.2 and BA.5 circulation in Korea. The effectiveness against critical infection was 67.7% (95% confidence interval, 50.7%-78.8%) at 31-60 days and 62.1% (95% confidence interval, 45.5%-73.7%) at 61-90 days.

Predictors of COVID-19 booster vaccine hesitancy among fully vaccinated adults in South Korea: a nationwide cross-sectional survey.

Objectives: To explore predictors of COVID-19 booster hesitancy among fully vaccinated young adults and parental factors on COVID-19 vaccine hesitancy for their children. Methods: A cross-sectional study was conducted via an online survey from December 2 to 20, 2021. We enrolled participants aged 18-49 years and elapsed ≥2 weeks after completing a primary series of COVID-19 vaccination. We estimated odds ratios (ORs) with 95% confidence intervals (CIs) using multivariate logistic regressions to evaluate factors associated with booster/vaccine hesitancy. Results: Among 2,993 participants, 48.8% indicated hesitancy (wait and see: 40.2%; definitely not: 8.7%). The booster hesitancy was more in females (OR 1.25, 95% CI 1.05-1.50), younger age group (1.44 [1.17-1.77] at 18-29 years vs. 40-49 years), lower education level (2.05 [1.10-3.82] in no high school vs. graduate degree), mRNA-1273 (2.01, 1.65-2.45 vs. BNT162b2), and those with serious adverse events following previous COVID-19 vaccination (2.03, 1.47-2.80). The main reasons for booster hesitancy were concerns about its safety (54.1%), followed by doubt about the efficacy (29.8%). Among 1,020 respondents who had children aged <18 years, 65.8% indicated COVID-19 vaccine hesitancy for their children; the hesitancy for children was higher at the younger age, and lower at lower education level, ChAdOx1 (vs. BNT162b2), and those with history of COVID-19 infection. Conclusion: Concerns on the efficacy and safety of COVID-19 vaccines were the major barrier to booster hesitancy. The initial COVID-19 vaccine type, younger age, women, lower education level, and adverse events following COVID-19 vaccine were the key predictors of booster hesitancy.

Estimated Effectiveness of Prior SARS-CoV-2 BA.1 or BA.2 Infection and Booster Vaccination Against Omicron BA.5 Subvariant Infection.

This case-control study estimates the effectiveness of prior SARS-CoV-2 BA.1 or BA.2 infection and booster vaccination against Omicron BA.5 subvariant infection.

Positive Predictive Value of Rapid Antigen Tests in School During SARS-CoV-2 Omicron Variant Surge.

In Korea, we conducted a national observational study to calculate the positive predictive value of SARS-CoV-2 rapid antigen tests in K-12 schools during the Omicron variant surge in March 2022. The weekly positive predictive value ranged from 86.4% to 93.2%. The positive predictive value was the highest among elementary school students with symptoms (95.7%) and lowest among teachers/staff without symptoms (70.9%).

Pediatric Deaths Associated With Coronavirus Disease 2019 (COVID-19) in Korea.

As of September 3, 2022, 5,388,338 coronavirus disease 2019 (COVID-19) cases and 46 deaths (3 in 2021 and 43 in 2022) were reported in children ≤ 18 years in Korea. Cumulative confirmed cases accounted for 67.3% of the population aged ≤ 18 years and case fatality rate was 0.85/100,000. Among 46 fatal cases, 58.7% were male and median age was 7 years. Underlying diseases were present in 47.8%; neurologic diseases (63.6%) and malignancy (13.6%) most common. Only four had history of COVID-19 immunization. COVID-19 associated deaths occurred at median 2 days from diagnosis (range: -1 to 21). Among COVID-19 deaths, 41.3% occurred before admission; 2 before hospital arrival and 17 in the emergency department. Among children whose cause was documented, myocarditis, respiratory and multiorgan failure were most common. COVID-19 associated death was seen early after diagnosis in children and public health policies to provide access to medical care for children with COVID-19 are essential during the pandemic.

Presumed population immunity to SARS-CoV-2 in South Korea, April 2022.

OBJECTIVES: We estimated the overall and age-specific percentages of the Korean population with presumed immunity against severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) as of April 2022 using the national registry. METHODS: We used the national coronavirus disease 2019 (COVID-19) infection and vaccination registry from South Korea, as described to define individuals with a previous history of COVID-19 infection, vaccination, or both, as persons with presumed immunity. RESULTS: Of a total of 53,304,627 observed persons, 24.4% had vaccination and infection, 58.1% had vaccination and no infection, 7.6% had infection and no vaccination, and 9.9% had no immunity. The SARS-CoV-2 Omicron variant emerged at a time when the presumed population immunity ranged from 80% to 85%; however, nearly half of the children were presumed to have no immunity. CONCLUSION: We report a gap in population immunity, with lower presumed protection in children than in adults. The approach presented in this work can provide valuable informed tools to assist vaccine policy-making at a national level.

A mixed methods study evaluating acceptability of a daily COVID-19 testing regimen with a mobile-app connected, at-home, rapid antigen test: Implications for current and future pandemics.

BACKGROUND: Widespread use of at-home rapid COVID-19 antigen tests has been proposed as an important public health intervention to interrupt chains of transmission. Antigen tests may be preferred over PCR because they provide on-demand results for relatively low cost and can identify people when they are most likely to be infectious, particularly when used daily. Yet the extent to which a frequent antigen testing intervention will result in a positive public health impact for COVID-19 will depend on high acceptability and high adherence to such regimens. METHODS: We conducted a mixed-methods study assessing acceptability of and adherence to a daily at-home mobile-app connected rapid antigen testing regimen among employees of a US-based media company. Acceptability was assessed across seven domains of the Theoretical Framework of Acceptability. RESULTS: Among 31 study participants, acceptability of the daily testing intervention was generally high, with participants reporting high perceived effectiveness, intervention coherence, and self-efficacy; positive affective attitude; acceptable degree of burden and opportunity cost; and assessing the intervention as ethical. 71% reported a preference to test daily using an at-home antigen test than weekly employment-based PCR. Mean adherence to the 21-day testing regimen was 88% with 43% of participants achieving 100% adherence, 48% testing at least every other day, and 10% testing less than every other day. CONCLUSIONS: Despite overall high acceptability and adherence, we identified three implementation challenges that must be addressed for frequent serial testing for COVID-19 to be implemented at scale and have a positive public health impact. First, users need guidance on how and when to adapt testing frequencies to different epidemiological conditions. Second, users and institutions need guidelines for how to safely store and share test results. Third, implementation of serial testing strategies must prioritize health equity and protect those most vulnerable to COVID-19.

Effectiveness of Second mRNA COVID-19 Booster Vaccine in Immunocompromised Persons and Long-Term Care Facility Residents.

We used a nationwide population registry in South Korea to estimate the effect of a second booster dose of mRNA COVID-19 vaccine on the risk for laboratory-confirmed SARS-CoV-2 infection, critical infection, and death in immunocompromised persons and long-term care facility (LTCF) residents. During February 16-May 7, 2022, among 972,449 eligible persons, 736,439 (75.7%) received a first booster and 236,010 (24.3%) persons received a second booster. Compared with the first booster group, at 30-53 days, the second booster recipients had vaccine effectiveness (VE) against all infections of 22.28% (95% CI 19.35%-25.11%), VE against critical infection of 56.95% (95% CI 29.99%-73.53%), and VE against death of 62.96% (95% CI 34.18%-79.15%). Our findings provide real-world evidence that a second booster dose of mRNA vaccine substantially increases protection against critical infection and death in these high-risk population groups.

Antiviral activity of canine interferon lambda 3 expressed using a recombinant adenovirus against canine coronavirus, canine parvovirus, and canine distemper virus.

Canine coronavirus (CCoV), canine parvovirus (CPV), and canine distemper virus (CDV) are highly contagious canine pathogens; dogs with these diseases are difficult to treat. In a previous study, we developed a recombinant adenovirus expressing canine interferon lambda 3 (Ad-caIFNλ3) in canine epithelial cells. In this study, we aimed to investigate the antiviral activity of Ad-caIFNλ3 against CCoV, CPV, and CDV in two canine cell lines, A72 and MDCK. Ad-caIFNλ3 transduction suppressed replication of these viruses without cytotoxicity. Our results suggest that Ad-caIFNλ3 may be a therapeutic candidate for canine viral diseases.

Social media may hinder learning about science; social media's role in learning about COVID-19.

Despite widespread concerns that misinformation is rampant on social media, little systematic and empirical research has been conducted on whether and how news consumption via social media affects people's accurate knowledge about COVID-19. Against this background, this study examines the causal effects of social media use on COVID-19 knowledge (i.e., both in the form of factual knowledge and misinformation detection) as well as the underlying mechanisms through which such effects occur. Based on original panel survey data across six weeks (W1 N = 1,363, W2 N = 752) in the U.S., we found that consuming news from social media fostered the perception that one need not actively seek news anymore because it would reach them anyway through their social connections (i.e., "news-finds-me" perception). This, in turn, can make one both uninformed and misinformed about COVID-19 issues. Furthermore, this mediated relationship is stronger among those who experience higher levels of information overload while on social media.

Reinfection with SARS-CoV-2 in general population, South Korea; nationwide retrospective cohort study.

To better understand the epidemiology of SARS-CoV-2 reinfections, we analyzed national data from South Korean who were followed longitudinally from January 2020 to April 2022. We conducted a nationwide retrospective cohort study to estimate possible SARS-CoV-2 reinfection rates in all residents in South Korea, with at least two episodes of laboratory-confirmed SARS-CoV-2 infection by reverse-transcriptase polymerase chain reaction or rapid antigen test (RAT) performed at least 45 or more days between both episodes, between January 2020 and April 2022. There were 16 130 855 laboratory-confirmed SARS-CoV-2 cases in South Korea, with 55 841 (346.2 per 100 000; or 0.3% of all infections) cases of possible reinfections. The reinfection rate has increased from 6.0 cases per 100 000 during Pre-Delta period to 128.0 cases per 100 000 and 355.1 cases per 100 000 during Delta and Omicron periods, respectively. Persons with one dose of vaccination had the highest reinfection rate of 642.2 per 100 000, followed by unvaccinated persons (536.2/100 000) and two-dose vaccinated persons (406.3/100 000). Our finding suggests that the majority of possible reinfections occurred following the emergence of new variants.

Clinical Significance of Antineutrophil Cytoplasmic Antibody Positivity in Patients Infected with SARS-CoV-2.

OBJECTIVES: To investigate the rate of antineutrophil cytoplasmic antibody (ANCA) positivity and its clinical significance in patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). METHODS: This study included 178 patients infected with SARS-CoV-2 who were enrolled in a cohort at a single centre. Myeloperoxidase (MPO)-ANCA and proteinase 3 (PR3)-ANCA levels in stored blood sera were measured using immunoassay kits. Mortality, mechanical ventilator care, and severe infection were assessed as three poor outcomes. The 2022 American College of Rheumatology and the European Alliance of Associations for Rheumatology (ACR/EULAR) classification criteria for the three subtypes of AAV were applied only to patients who had MPO-ANCA or PR3-ANCA among study subjects. RESULTS: The detection rate of ANCA positivity was 18.5%. MPO-ANCA and PR3-ANCA were found in 22 (12.4%) and 14 (7.9%) patients, respectively. However, neither MPO-ANCA nor PR3-ANCA affected the three poor outcomes. According to the new criteria, 12 (6.7%) and 21 (11.8%) patients were classified as having granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA), respectively. CONCLUSIONS: SARS-CoV-2 infection may increase the rate of ANCA positivity. Although it might not affect poor outcomes, it might contribute to the classification of GPA and MPA despite uncertain clinical significance.

Birmingham vasculitis activity score and the short form 36-item health survey predict current depressive disorders in patients with antineutrophil cytoplasmic antibody-associated vasculitis during the SARS-CoV-2 pandemic.

INTRODUCTION: This study compared the frequency and severity of depressive disorders in patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV) before and during the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) pandemic using the Korean version of the Center for Epidemiologic Studies Depression Scale-Revised (K-CESD-R) and the Korean version of the Profile of Mood States (K-POMS) depression, and further determined predictors of current depressive disorders in the patients during the pandemic. METHODS: Of the 61 patients with AAV who participated before the pandemic, 8 patients were transferred to other hospitals, 3 patients died, and 2 patients refused to participate in this study. Finally, 48 patients participated in this study. Depression disorders were defined as K­CESD-R ≥ 16. RESULTS: When comparing the patterns of mental health between patients with AAV before and during the pandemic, no change in K­CESD­R or K­POMS subscale scores was observed. Among AAV-related indices, regardless of the pandemic, the short-form 36-item Health Survey (SF-36) mental component score (MCS) and physical component score (PCS) were significantly correlated with K­CESD­R and could predict current depressive disorders. When the cut-off of Birmingham vasculitis activity score (BVAS) for depressive disorders was obtained by the receiver operator characteristic curve, it significantly predicted current depressive disorders in patients with AAV during the pandemic, unlike those before the pandemic. CONCLUSION: We verified that SF-36 MCS and PCS could predict current depressive disorders, regardless of the pandemic, and furthermore, we demonstrated for the first time that BVAS was a predictor of current depressive disorders in patients with AAV during the pandemic unlike those before the pandemic.

Impact of national Covid-19 vaccination Campaign, South Korea.

BACKGROUND: We evaluate the overall effectiveness of the nationwide vaccination campaign using ChAdOx1 nCoV-19, BNT162b2, mRNA-1273, and Ad26.COV2.S vaccines in preventing Covid-19 in South Korea. METHODS: The National Surveillance System with the National Immunization Registry were linked to form a large-linked database for assessment. Age-adjusted incidence of SARS-CoV-2 infection, severe disease, and death by vaccination status are calculated. Weekly vaccine effectiveness was calculated based on incidence rate ratio (IRR) between fully-vaccinated and unvaccinated persons, as: IRR = incidence rate of vaccinated / incidence rate of unvaccinated. We estimate the cumulative SARS-CoV-2 outcome overtime comparing the observed case with predicted cases without vaccination. RESULTS: Age-adjusted incidence in unvaccinated persons (5.69 per 100,000 person-day) was 2.7 times the rate in fully vaccinated (2.13 per 100,000 person-day) persons, resulting effectiveness against SARS-CoV-2 infection of 63%. Vaccine effectiveness against severe disease and death were 93% and 95%, respectively. Between March and October 2021, estimated Covid-19 related outcomes averted by vaccinations were: 46,508 infections, 3,424 severe diseases, and 718 deaths. CONCLUSIONS: We found significant protection for national Covid-19 vaccination campaign against Covid-19 severe disease, and death in target populations, but there was an unexpected decreased protection against SARS-CoV-2 infection, highlighting the importance of continued surveillance and assessment.