COVID-19 Vaccination in Korea: Past, Present, and the Way Forward

Synergistic Effect of SARS-CoV-2 Infection and COVID-19 Vaccination on the Risk of Venous Thromboembolism

BACKGROUND

Previous studies have reported a greater risk of venous thromboembolism among patients infected with SARS-CoV-2 and those who received COVID-19 vaccination. Nevertheless, there is a lack of understanding regarding the interaction effect on the risk of venous thromboembolism occurrence between SARS-CoV-2 infection and COVID-19 vaccination.

METHODS

This was a retrospective cohort study including adult patients with confirmed SARS-CoV-2 infection between October 2020 and September 2021. Patients with confirmed SARS-CoV-2 infection were selected and matched 1:1 by age and sex with individuals who were not infected during the same period. A Cox proportional hazards model was used to analyze the venous thromboembolism risk.

RESULTS

The study included 422546 individuals who were divided into 4 groups; the interaction group defined by having SARS-CoV-2 infection within 90 days following COVID-19 vaccination, the infection group defined by no vaccination before 90 days of SARS-CoV-2 infection, the vaccination group defined by COVID-19 vaccination without SARS-CoV-2 infection, and the reference group defined by neither COVID-19 vaccination nor SARS-CoV-2 infection. The results showed that the adjusted hazard ratio (aHR) of the interaction group was 29.71 (95% confidence interval [CI], 22.95-38.47), while the aHRs of the infection group and the vaccination group were 6.66 (95% CI, 5.18-8.58) and 2.31 (95% CI, 1.78-3.00), respectively.

CONCLUSIONS

A synergistic effect on the risk of venous thromboembolism was suggested when individuals were infected with SARS-CoV-2 within 90 days following COVID-19 vaccination.

Coronavirus disease-2019 (COVID-19) outbreak in a long-term care hospital in Korea in early 2021

Background

This study describes the outbreak investigations and control measures for a coronavirus disease 2019 (COVID-19) outbreak at a long-term care hospital (LTCH) in Seoul.

Methods

The outbreak occurred from February 24, 2021 to March 2, 2021 at a 228-bed LTCH in Seoul. Monitoring of the outbreak continued until March 16, 2021. The LTCH investigated the outbreak in cooperation with the district public health centre. After approval from the institutional review board, the hospital's COVID-19 outbreak-related data were collected and analysed.

Results

The outbreak commenced when a new caregiver tested positive for COVID-19 in routine employee screening tests. During this outbreak, eight of 342 people including 175 patients and 64 caregivers were positive for the COVID-19 virus SARS-CoV-2. The mean age of the confirmed cases was 75.1 years (range 55-90). Of the eight, four (50%) were males; two (25%) were caregivers; six (75%) were asymptomatic; six (75%) had previously visited a rehabilitation centre, which was located on the basement level; and one visited different hospitals' outpatient clinics. Three of the 22 environmental specimens were test-positive at the corridor's handrail and the bed rails of confirmed patients. The outbreak ended with the immediate transfer of the confirmed cases to hospitals dedicated to infectious diseases and the transfer of close contacts of these cases to designated hospitals which were organised by the health authorities.

Conclusions

We found a potential link between the rehabilitation centre and the outbreak. To prevent future outbreaks at LTCHs, it is necessary to enhance each LTCH's infection control resources and competencies based on its specific requirements, with support from the government.

Disparities in COVID-19 vaccine coverage and risk factors among individuals with disabilities

BACKGROUND

Vaccination is a crucial strategy in responding to infectious diseases. We investigated the COVID-19 vaccination coverage among people with disabilities compared to people without disabilities. We identified risk factors of under-vaccination and vulnerable subgroups.

OBJECTIVES

To assess COVID-19 vaccination coverage in individuals with disabilities compared with individuals without disabilities and identify risk factors for under-vaccination.

METHODS

This cross-sectional study analysed the Korea Disease Control and Prevention Agency-COVID-19-National Health Insurance Service (K-COV-N) cohort, which registered adults with disabilities in 2020 and age and sex-matched individuals without disabilities were included. Vaccination records from the rollout through March 31, 2022 were analysed. Multivariable ordinal logistic regression models were employed.

RESULTS

This study included 4,811,866 participants after exclusions. Within the same disability type, individuals with severe disabilities had higher non-vaccination rates than those with mild disabilities. Individuals with pulmonary, brain and cardiac disabilities exhibited higher age-standardized non-vaccination rates (16.7 %, 15.1 % and 12.5 %, respectively). individuals with disabilities were more likely to be under-vaccinated than those without disabilities, with an adjusted odds ratio (aOR) of 1.01 (95 % CI 1.01-1.02). Females consistently exhibited a higher likelihood of non-vaccination in all subgroups. The impact of age differed based on the disability subgroups. The likelihood of under-vaccination was low in employee-insured individuals.

CONCLUSIONS

Individuals with disabilities were less likely to receive COVID-19 vaccination compared with those without disabilities and variations were observed by disability types. Tailored strategies considering identified risk factors are required to ensure equal vaccination access for individuals with disabilities in future pandemics.

COVID-19 vaccine acceptance and 5C psychological antecedents amid the omicron surge in South Korea and China

BACKGROUND

It is crucial to emphasize the necessity of annual COVID-19 vaccination, particularly for vulnerable populations like older and chronically ill individuals.

OBJECTIVES

This study aimed to quantify the level of vaccination acceptance and its 5C psychological antecedents in the South Korean and Chinese populations and also to identify the predictors, considering contextual variations that influence vaccine acceptance in both countries.

METHODS

A cross-sectional survey study was undertaken in South Korea and China between March 15 and March 30, 2023, coinciding with the emergence of the SARS-CoV-2 Omicron variant in both nations. The study comprised 1000 participants from South Korea and 3000 participants from China. A chi-square analysis, t-tests and multivariable logistic regression analysis were employed to evaluate the factors influencing the acceptance of COVID-19 vaccines.

RESULTS

A higher degree of vaccine acceptance was observed among Chinese participants (48.5 %), in contrast to the 16.8 % among South Koreans. Analyzing the psychological antecedents for vaccination, the Chinese cohort showed high vaccine confidence, whereas South Koreans had increased constraint perceptions. Psychological antecedents, particularly Confidence, play a significant positive role in vaccine acceptance in both South Korea (OR 2.98, CI [2.26-4.01], p < 0.001) and China (OR 2.93, CI [2.58-3.33], p < 0.001), while Constraints in South Korea (OR 0.83, CI [0.69-0.99], p < 0.05) and China (OR 0.86, CI [0.79-0.94], p < 0.001) contribute negatively to vaccine acceptance. Notably, divergent trends in the impact of age and underlying health conditions on vaccine acceptance were observed.

CONCLUSIONS

This study reveals a substantial disparity in acceptance, psychological antecedents, and predictors of vaccine acceptance between China and South Korea. This importance of understanding contextual factors influencing public vaccine acceptance is emphasized. There is an urgent need for robust vaccination strategies that boost confidence and alleviate constraints to COVID-19 vaccination, which should be tailored to the unique contextual factors of each country.

Comparison of the efficacy of COVID-19 responses in South Korea and the United States

BACKGROUND

The COVID-19 pandemic devastated many countries worldwide by causing large numbers of fatalities. In our research, we wanted to answer the question: Why was there such a large difference in the mortality rate between South Korea and the United States? This is because many East Asian countries, such as Korea, had a lower mortality rate than many countries, including developed ones, across the world - the mortality rate of South Korea was about five times lower than the United States.

METHODS

This study comprehensively compares strategies used to address the COVID-19 pandemic in two different countries: South Korea and the United States. The various aspects of these two countries' responses are examined, including initial response, information dissemination and public compliance, mitigation strategies, and vaccine rollout and their impacts.

RESULTS

Early and widespread testing, rigorous contact tracing, the clear release of government information, and an organized vaccine rollout powered a proactive approach in South Korea. The United States had a contrasting response consisting of delayed and more decentralized measures, where testing lagged due to varying policies and the political controversies facing vaccine distribution.

CONCLUSIONS

We signify the gravity of rapid response and testing, clear communication, and efficient vaccine distribution, as we believe this could correlate with a lower mortality rate. In addition, we discuss future directions, including the need for a specific health infrastructure and protocol against highly infectious outbreaks.

Risk for Facial Palsy after COVID-19 Vaccination, South Korea, 2021-2022

We conducted a self-controlled case series study to investigate the association between COVID-19 vaccination and facial palsy (FP) in South Korea. We used a large immunization registry linked with the national health information database. We included 44,564,345 patients >18 years of age who received >1 dose of COVID-19 vaccine (BNT162b2, mRNA-1273, ChAdOx1 nCoV-19, or Ad.26.COV2.S) and had an FP diagnosis and corticosteroid prescription within 240 days postvaccination. We compared FP incidence in a risk window (days 1-28) with a control window (the remainder of the 240-day observation period, excluding any risk windows). We found 5,211 patients experienced FP within the risk window and 10,531 experienced FP within the control window. FP risk increased within 28 days postvaccination, primarily after first and second doses and was observed for both mRNA and viral vaccines. Clinicians should carefully assess the FP risk-benefit profile associated with the COVID-19 vaccines and monitor neurologic signs after vaccination.

The potential role of perceived neighborhood social cohesion on COVID-19 vaccination uptake among individuals aged 50 and older: Results from the Korean Community Health Survey

The COVID-19 pandemic highlighted the critical importance of vaccination in controlling infectious diseases. While previous research has identified social cohesion as a potential facilitator of health behaviors, empirical studies exploring its direct impact on COVID-19 vaccination rates, especially across different age groups, remain limited. This cross-sectional study utilized data from the 2021 Korean Community Health Survey, a nationally representative survey conducted in South Korea. The analysis focused on adults aged 50 and older, categorizing them into two age groups (50-64 and ≥65). We investigated the association between perceived neighborhood social cohesion and COVID-19 vaccination status, controlling for socio-economic status, health behaviors, and concerns related to COVID-19. Statistical analysis was conducted using complex sample multiple logistic regression to adjust for potential confounders. The study included 135,352 participants, with an analysis showing that in the age group ≥65, higher levels of perceived neighborhood social cohesion were significantly associated with increased vaccination uptake (aOR for trust between neighbors: 1.200, 95% CI: 1.058-1.362; aOR for mutual assistance among neighbors: 1.491, 95% CI: 1.312-1.695). Interestingly, these associations were not significant in the 50-64 age group. Additionally, satisfaction with healthcare services was associated with higher vaccination uptake in both age groups (aOR: 1.106, 95% CI: 1.004-1.219 for 50-64; aOR: 1.306, 95% CI: 1.160-1.471 for ≥65). Our findings suggest that perceived neighborhood social cohesion plays a crucial role in influencing COVID-19 vaccination uptake among older adults, particularly those aged 65 and above. These results indicate that health policies aimed at enhancing social cohesion may effectively improve vaccination rates, especially among the elderly. Future research should explore the impact of social cohesion on other age groups and assess the causal relationships in longitudinal studies.

Factors Associated with Treatment Satisfaction in Korean Patients with Psoriasis

Purpose

Treatment satisfaction among patients with psoriasis can vary significantly based on available treatment options and individual patient characteristics.

Patients and Methods

This cross-sectional study utilized psoriasis-specific questionnaires to assess treatment satisfaction and identify the factors associated with treatment satisfaction in Korean patients. The study included 350 eligible patients aged 19 or older from a nationwide psoriasis group. Participants completed a self-reported web-based questionnaire assessing socioeconomic and clinical status, quality of life, and treatment satisfaction. Linear regression models were employed to analyze the factors associated with treatment satisfaction.

Results

The results showed that patients with mild to moderate psoriasis, as determined by the body surface area involvement, had higher satisfaction scores for treatment effectiveness. Moreover, patients receiving biologic therapies reported significantly higher total satisfaction scores and scores across all domains than those not utilizing biologics. However, patients reporting poorer quality of life or experiencing anxiety exhibited lower satisfaction scores.

Conclusion

Findings suggest that while biologic treatments may confer greater satisfaction to patients with psoriasis, diminished quality of life and anxiety can negatively impact satisfaction levels. The study underscores the importance of understanding the factors associated with patient satisfaction to optimize treatment outcomes in psoriasis management.

Preoperative COVID-19 and Postoperative Mortality in Cancer Surgery: A South Korean Nationwide Study

BACKGROUND

We evaluated the impact of preoperative COVID-19 on early postoperative mortality in patients undergoing time-sensitive cancer surgery.

METHODS

This retrospective, nationwide cohort study included adult patients who underwent various cancer (thyroid, breast, stomach, colorectal, hepatobiliary, genitourinary, lung, and multiple cancer) surgeries under general anesthesia in South Korea in 2022. Patients were grouped according to the duration from the date of COVID-19 confirmation to the date of surgery (0-2 weeks, 3-4 weeks, 5-6 weeks, and ≥7 weeks). Patients without preoperative COVID-19 also were included. Multivariable logistic regression analysis with Firth correction was performed to investigate the association between preoperative COVID-19 and 30-day and 90-day postoperative mortality. The covariates encompassed sociodemographic factors, the type of surgery, and vaccination status in addition to the aforementioned groups.

RESULTS

Of the 99,555 patients analyzed, 30,933 (31.1%) were preoperatively diagnosed with COVID-19. Thirty-day mortality was increased in those who underwent surgery within 0-2 weeks after diagnosis of COVID-19 (adjusted odds ratio [OR], 1.47; 95% confidence interval [CI], 1.02-2.12; P = 0.038); beyond 2 weeks, there was no significant increase in mortality. A similar pattern was observed for 90-day mortality. Full vaccination against COVID-19 was associated with reduced 30-day (OR 0.38; 95% CI 0.29-0.50; P < 0.001) and 90-day (OR 0.39; 95% CI 0.33-0.46; P < 0.001) mortality.

CONCLUSIONS

Cancer surgery within 2 weeks of COVID-19 diagnosis was associated with increased early postoperative mortality. These findings support current guidelines that recommend postponing elective surgery for at least 2 weeks after the diagnosis of COVID-19.

Persistent differences in the immunogenicity of the two COVID-19 primary vaccines series, modulated by booster mRNA vaccination and breakthrough infection

INTRODUCTION

The long-term impact of initial immunogenicity induced by different primary COVID-19 vaccine series remains unclear.

METHODS

A prospective cohort study was conducted at 10 tertiary hospitals in Korea from March 2021 to September 2022. Immunogenicity assessments included anti-spike protein antibody (Sab), SARS-CoV-2-specific interferon-gamma releasing assay (IGRA), and multiplex cytokine assays for spike protein-stimulated plasma. Spike proteins derived from wild-type SARS-CoV-2 and alpha variant (Spike1) and beta and gamma variant (Spike2) were utilized.

RESULTS

A total of 235 healthcare workers who had received a two-dose primary vaccine series of either ChAdOx1 or BNT162b2, followed by a third booster dose of BNT162b2 (166 in the ChAdOx1/ChAdOx1/BNT162b2 (CCB) group and 69 in the BNT162b2/BNT162b2/BNT162b2 (BBB) group, based on the vaccine series) were included. Following the primary vaccine series, the BBB group exhibited significantly higher increases in Sab levels, IGRA responses, and multiple cytokines (CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1β, interleukin (IL)-1ra, IFN-γ, IL-2, IL-4, and IL-10) compared to the CCB group (all P < 0.05). One month after the third BNT162b2 booster, the CCB group showed Sab levels comparable to those of the BBB group, and both groups exhibited lower levels after six months without breakthrough infections (BIs). However, among those who experienced BA.1/2 BIs after the third booster, Sab levels increased significantly more in the BBB group than in the CCB group (P < 0.001). IGRA responses to both Spike1 and Spike2 proteins were significantly stronger in the BBB group than the CCB group after the third booster, while only the Spike2 response were higher after BIs (P = 0.007). The BBB group exhibited stronger enhancement of T-cell cytokines (IL-2, IL-4, and IL-17A) after BIs than in the CCB group (P < 0.05).

CONCLUSION

Differences in immunogenicity induced by the two primary vaccine series persisted, modulated by subsequent booster vaccinations and BIs.

Cardiovascular Safety of COVID-19 Vaccination in Patients With Cancer: A Self-Controlled Case Series Study in Korea

BACKGROUND

Cancer patients have an increased risk of cardiovascular outcomes and are susceptible to coronavirus disease 2019 (COVID-19) infection. We aimed to assess the cardiovascular safety of COVID-19 vaccination for cancer patients in South Korea.

METHODS

We conducted a self-controlled case series study using the K-COV-N cohort (2018-2021). Patients with cancer aged 12 years or older who experienced cardiovascular outcomes were identified. Cardiovascular outcomes were defined as myocardial infarction, stroke, venous thromboembolism (VTE), myocarditis, or pericarditis, and the risk period was 0-28 days after receiving each dose of COVID-19 vaccines. A conditional Poisson regression model was used to calculate the incidence rate ratio (IRR) with 95% confidence interval (CI).

RESULTS

Among 318,105 patients with cancer, 4,754 patients with cardiovascular outcomes were included. The overall cardiovascular risk was not increased (adjusted IRR, 0.99 [95% CI, 0.90-1.08]) during the whole risk period. The adjusted IRRs of total cardiovascular outcomes during the whole risk period according to the vaccine type were 1.07 (95% CI, 0.95-1.21) in the mRNA vaccine subgroup, 0.99 (95% CI, 0.83-1.19) in the ChAdOx1 nCoV-19 vaccine subgroup, and 0.86 (95% CI, 0.68-1.10) in the mix-matched vaccination subgroup. However, in the analysis of individual outcome, the adjusted IRR of myocarditis was increased to 11.71 (95% CI, 5.88-23.35) during the whole risk period. In contrast, no increased risk was observed for other outcomes, such as myocardial infarction, stroke, VTE, and pericarditis.

CONCLUSION

For cancer patients, COVID-19 vaccination demonstrated an overall safe profile in terms of cardiovascular outcomes. However, caution is required as an increased risk of myocarditis following COVID-19 vaccination was observed in this study.

Effectiveness of COVID-19 vaccines against severe outcomes in cancer patients: Real-world evidence from self-controlled risk interval and retrospective cohort studies

BACKGROUND

The effectiveness of COVID-19 vaccines is generally reduced in cancer patients compared to the general population. However, there are only a few studies that compare the relative risk of breakthrough infections and severe COVID-19 outcomes in fully vaccinated cancer patients versus their unvaccinated counterparts.

METHODS

To assess the effectiveness of COVID-19 vaccines in cancer patients, we employed (1) a self-controlled risk interval (SCRI) design, and (2) a retrospective matched cohort design. A SCRI design was used to compare the risk of breakthrough infection in vaccinated cancer patients during the period immediately following vaccination ("control window") and the period in which immunity is achieved ("exposure windows"). The retrospective matched cohort design was used to compare the risk of severe COVID-19 outcomes between vaccinated and unvaccinated cancer patients. For both studies, data were extracted from the Korea Disease Control and Prevention Agency-COVID-19-National Health Insurance Service cohort, including demographics, medical history, and vaccination records of all individuals confirmed with COVID-19. We used conditional Poisson regression to calculate the incidence rate ratio (IRR) for breakthrough infection and Cox regression to estimate the hazard ratio (HR) for severe outcomes.

RESULTS

Of 14,448 cancer patients diagnosed with COVID-19 between October 2020 and December 2021, a total of 217 and 3996 cancer patients were included in the SCRI and cohort study respectively. While the risk of breakthrough infections, measured by the incidence rate in the control and exposure windows, did not show statistically significant difference in vaccinated cancer patients (IRR=0.88, 95% CI: 0.64-1.22), the risk of severe COVID-19 outcomes was significantly lower in vaccinated cancer patients compared to those unvaccinated (HR=0.27, 95% CI: 0.22-0.34).

CONCLUSION

COVID-19 vaccines significantly reduce the risk of severe outcomes in cancer patients, though their efficacy against breakthrough infections is less evident.

The Impact of the COVID-19 Pandemic on Bell's Palsy and Ramsay-Hunt Syndrome: A Multicenter Retrospective Study

BACKGROUND

This article presents a comprehensive review of data on the impact of facial palsy during the coronavirus disease 2019 (COVID-19) pandemic. The possible causes and pathophysiological mechanisms of changes in the epidemiology of facial palsy during the COVID-19 pandemic are also discussed.

METHODS

This multicenter retrospective cohort study included 943 patients diagnosed with Bell's palsy or Ramsay Hunt syndrome. This study compared patient demographics, comorbidities, symptoms, and treatments before the COVID-19 pandemic (from 2017 to 2019) and during the COVID-19 pandemic, from 2020 to 2022).

RESULTS

Following the COVID-19 outbreak, there has been a significant increase in the number of cases of Bell's palsy, particularly among elderly individuals with diabetes. Bell's palsy increased after the COVID-19 outbreak, rising from 75.3% in the pre-COVID-19 era to 83.6% after the COVID-19 outbreak. The complete recovery rate decreased from 88.2% to 73.9%, and the rate of recurrence increased from 2.9% to 7.5% in patients with Bell's palsy. Ramsay Hunt syndrome showed fewer changes in clinical outcomes.

CONCLUSION

This study highlights the impact of the COVID-19 pandemic on the presentation and management of facial palsy, and suggests potential associations with COVID-19. Notably, the observed increase in Bell's palsy cases among elderly individuals with diabetes emphasizes the impact of the pandemic. Identifying the epidemiological changes in facial palsy during the COVID-19 pandemic has important implications for assessing its etiology and pathological mechanisms of facial palsy disease.

Effect of COVID-19 infection and vaccination on SARS-CoV-2 antibody titer change following ovarian stimulation: Prospective analysis of IVF outcomes

The coronavirus disease 2019 (COVID-19) outbreak caused by SARS-CoV-2 (severe acute respiratory syndrome coronavirus-2) has affected various medical fields worldwide. However, relatively few studies have examined the impact of COVID-19 infection and vaccination on in vitro fertilization (IVF) outcomes and changes in SARS-CoV-2 antibody concentration in follicular fluid (FF). A total of 45 women were prospectively recruited and assigned to 3 groups: uninfected and non-vaccinated control group (Control group), infected group (COVID + group), and vaccinated group (Vaccination group). Serum and follicular fluid (FF) estradiol, progesterone, and SARS-CoV-2 antibody concentrations were measured. There were no statistical differences in the total number of retrieved oocytes (P = .291), mature oocytes (P = .416), and good-quality embryos (P = .694) among the 3 groups. In the vaccination group, BNT162b2 exhibited a significantly lower trigger-day serum estradiol/MII oocyte level (110.6 pg/mL) than other vaccines (289.5 pg/mL) (P = .006). No statistical differences in serum (P = .687) and FF (P = .108) SARS-CoV-2 antibody changes were noted among the 3 groups. Only FF antibody changes exhibited statistically significant differences between the BNT162b2 and other vaccine subgroups (P = .047). COVID-19 infection and vaccination do not affect IVF outcomes. However, the effect of BNT162b2 on steroidogenesis of the mature oocyte and FF SARS-CoV2 antibody titer should be further investigated.

Correlation of geopolitics, education, democracy with COVID-19 vaccination rate

INTRODUCTION

Vaccine hesitancy is an ongoing problem and determining the factors that increase the vaccination rate in various countries of the world might be useful for further implementation of efficient public health policies and negating anti-vaccination campaigns.

MATERIALS AND METHODS

Human Development Index (HDI), Education Index (EI), Democracy Index (DI), COVID-19 vaccination rates, COVID-19 data were collected from public sources such as UNDP - Human Development Reports, UNESCO - Education Index, Economist Intelligence, WHO- COVID-19 Dashboard, Our World In Data, The Financial Times COVID-19 Dashboard. Statistical analysis such as Pearson correlation, and linear regression analyses were done to determine a relation between the above-mentioned indices and COVID-19 vaccination rates (1-dose, 2-dose, booster, and combined).

RESULTS

HDI had the strongest positive correlation with the vaccination rates (1-dose- r (181) = 0.632, p < 0.001, 2-dose- r (181) = 0.671, p < 0.001, booster- r (181) = 0.718, p < 0.001, combined- 0.703, p < 0.001). EI (1-dose- r (177) = 0.560, p < 0.001, 2-dose- r (177) = 0.599, p < 0.001, booster- r (177) = 0.642, p < 0.001, combined- 0.626, p < 0.001), DI (1-dose- r (163) = 0.445, p < 0.001, 2-dose- r (163) = 0.479, p < 0.001, booster- r (163) = 0.534, p < 0.001, combined- 0.508, p < 0.001), as well as Geographic location (1-dose- η (Eta) = 0.610 p < 0.001, 2-dose- η (Eta) = 0.633 p < 0.001, booster- η (Eta) = 0.657, p < 0.001, combined- η (Eta) = 0.645, p < 0.001) had positive correlation with vaccination rates.

CONCLUSION

There is a strong positive correlation of COVID-19 vaccination rates with HDI and EI.

Magnitude and Duration of Serum Neutralizing Antibody Titers Induced by a Third mRNA COVID-19 Vaccination against Omicron BA.1 in Older Individuals

BACKGROUND

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant (B.1.1.529) is dominating coronavirus disease 2019 (COVID-19) worldwide. The waning protective effect of available vaccines against the Omicron variant is a critical public health issue. This study aimed to assess the impact of the third COVID-19 vaccination on immunity against the SARS-CoV-2 Omicron BA.1 strain in older individuals.

MATERIALS AND METHODS

Adults aged ≥60 years who had completed two doses of the homologous COVID-19 vaccine with either BNT162b2 (Pfizer/BioNTech, New York, NY, USA, BNT) or ChAdOx1 nCoV (SK bioscience, Andong-si, Gyeongsangbuk-do, Korea, ChAd) were registered to receive the third vaccination. Participants chose either BNT or mRNA-1273 (Moderna, Norwood, MA, USA, m1273) mRNA vaccine for the third dose and were categorized into four groups: ChAd/ChAd/BNT, ChAd/ChAd/m1273, BNT/BNT/BNT, and BNT/BNT/m1273. Four serum specimens were obtained from each participant at 0, 4, 12, and 24 weeks after the third dose (V1, V2, V3, and V4, respectively). Serum-neutralizing antibody (NAb) activity against BetaCoV/Korea/KCDC03/2020 (NCCP43326, ancestral strain) and B.1.1.529 (NCCP43411, Omicron BA.1 variant) was measured using plaque reduction neutralization tests. A 50% neutralizing dilution (ND50) >10 was considered indicative of protective NAb titers.

RESULTS

In total, 186 participants were enrolled between November 24, 2021, and June 30, 2022. The respective groups received the third dose at a median (interquartile range [IQR]) of 132 (125 - 191), 123 (122 - 126), 186 (166 - 193), and 182 (175 - 198) days after the second dose. Overall, ND50 was lower at V1 against Omicron BA.1 than against the ancestral strain. NAb titers against the ancestral strain and Omicron BA.1 variant at V2 were increased at least 30-fold (median [IQR], 1235.35 [1021.45 - 2374.65)] and 129.8 [65.3 - 250.7], respectively). ND50 titers against the ancestral strain and Omicron variant did not differ significantly among the four groups (P = 0.57). NAb titers were significantly lower against the Omicron variant than against the ancestral strain at V3 (median [IQR], 36.4 (17.55 - 75.09) vs. 325.9 [276.07 - 686.97]; P = 0.012). NAb titers against Omicron at V4 were 16 times lower than that at V3. Most sera exhibited a protective level (ND50 >10) at V4 (75.0% [24/32], 73.0% [27/37], 73.3% [22/30], and 70.6% [12/17] in the ChAd/ChAd/BNT, ChAd/ChAd/m1273, BNT/BNT/BNT, and BNT/BNT/m1273 groups, respectively), with no significant differences among groups (P = 0.99).

CONCLUSION

A third COVID-19 mRNA vaccine dose restored waning NAb titers against Omicron BA.1. Our findings support a third-dose vaccination program to prevent the waning of humoral immunity to SARS-CoV-2.

Pneumonia Prevalence Upon Chest Radiography According to Vaccination Status Among Patients Under 50 Years of Age With Coronavirus Disease 2019

BACKGROUND

Coronavirus disease 2019 (COVID-19) vaccination is effective in preventing the disease transmission and progression. However, the relatively mild disease course of the omicron variant and the decrease in antibodies over time after vaccination raise questions about the effectiveness of vaccination, especially in young people. We compared the prevalence of pneumonia and chest X-ray severity score according to vaccination status among patients < 50 years old with COVID-19.

METHODS

From January 17 to March 17, 2022, 579 patients with COVID-19, who were < 50 years old and had a known vaccination history in our institution, were all included in this study. All patients underwent initial chest radiography, and follow-up chest radiographs were obtained every two days until discharge. Pneumonia was scored from the radiographs using the Brixia scoring system. The scores of the six lung zones were added for a total score ranging from 0 to 18. Patients were divided into four groups according to 10-year age intervals. Differences between groups were analyzed using the χ² or Fisher's exact tests for categorical variables and the Kruskal-Wallis test or analysis of variance for continuous variables.

RESULTS

Among patients aged 12-19 years, the prevalence of pneumonia did not differ depending on vaccination status (non-vaccinated vs. vaccinated, 1/47 [2.1%] vs. 1/18 [5.6%]; P = 0.577). Among patients in their 20s, the prevalence of pneumonia was significantly higher among non-vaccinated patients than among vaccinated patients (8/28, 28.6% vs. 7/138, 5.1%, P < 0.001), similar to patients in their 40s (32/52 [61.5%] vs. 18/138 [13.0%]; P < 0.001). The chest X-ray severity score was also significantly higher in non-vaccinated patients than that in vaccinated patients in their 20s to their 40s (P < 0.001), but not among patients aged 12-19 years (P = 0.678).

CONCLUSION

In patients aged 20-49 years, vaccinated patients had a significantly lower prevalence of pneumonia and chest X-ray severity score than non-vaccinated patients.

Establishment of Safety Monitoring System for Vaccines Not Included in the National Immunization Program in Korea

BACKGROUND

In Korea, there are no surveillance programs for vaccines that are not included in the national immunization program (NIP), and vaccine safety monitoring in the adult population is inadequate. This study aimed to establish a safety monitoring system for non-NIP vaccines in adults.

METHODS

Frequently administered non-NIP vaccines were selected. Individuals were included if they received at least one of the selected vaccines at a participating institution and provided informed consent. Solicited and unsolicited adverse events were monitored using questionnaires sent through text messages on days 1, 3, 7, 28, and 90 post-vaccination. Selected adverse events of special interest (AESIs) were monitored monthly by retrospective review of electronic medical records. Causality was assessed according to the Korea Disease Control and Prevention Agency guidelines.

RESULTS

Four vaccines (tetanus-diphtheria-pertussis [Tdap], pneumococcal conjugate 13-valent [PCV13], live zoster vaccine [ZVL], and recombinant zoster vaccine [RZV]) were selected, and their safety profiles were monitored at four tertiary hospitals and 10 primary care clinics. The response rates of the questionnaires on post-vaccination days 1, 7, 28, and 90 were 99.2%, 93.6%, 81.0%, and 48.7%, respectively. Of 555 AESI identified over 10 months, 10 cases received one of the selected non-NIP vaccines within 90 days of the event.

CONCLUSION

We are establishing the first safety monitoring system for selected non-NIP vaccines in Korea since September 2022 and report its progress as of July 2023. However, continuous government support is essential for its maintenance and improvement.

Mortality Rate and Outcomes of Omicron Variant Positive Patients with Osteoporotic Fractures: A Retrospective Study

BACKGROUND

During the lockdown period associated with the coronavirus disease 2019 (COVID-19) pandemic, increased mortality rates among patients with COVID-19 have been reported. This study aimed to analyze the mortality rate of osteoporotic hip fractures in patients who were COVID-19-positive after the lockdown during the Omicron period.

METHODS

A retrospective study was performed with 194 patients who were aged 70 years or more and diagnosed with osteoporotic hip fracture. The patients were divided into two groups according to their COVID-19 diagnoses. Surgery was performed within 10 days of diagnosis. Age, sex, past medical history, time until surgery, postoperative complications, and the primary outcome of mortality rate at 30 and 90 days were analyzed.

RESULTS

Among the 194 patients, 13 and 181 were in the COVID-19-positive and negative group, respectively. The total, 30-day, and 90-day mortality rates in the control and COVID-positive group were 11% and 0% (P=0.368), 1.7% and 0% (P=1.000), and 5.0% and 0% (P=1.000), respectively. No significant differences were observed in age, sex, history, time to surgery, postoperative complications, or postoperative mortality. In 1:1 propensity score matching, the time to surgery was 5.34 days in patients who were COVID-19-positive, and 3.00 days in patients who were COVID-19 negative, with no statistical significance (P=0.09). Age, sex, medical history, postoperative complications, and postoperative mortality were not significantly different between the groups.

CONCLUSIONS

Regardless of the COVID-19 diagnosis, surgical treatment without delay is believed to result in positive outcomes in older patients with osteoporotic hip fractures, as no significant differences in mortality rate and respiratory complications were observed between patients who were COVID-19-positive and those who were COVID-19 negative.

Trends in Research on Patients With COVID-19 in Korean Medical Journals

OBJECTIVES

This study was conducted to systematically summarize trends in research concerning patients with coronavirus disease 2019 (COVID-19) as reported in Korean medical journals.

METHODS

We performed a literature search of KoreaMed from January 2020 to September 2022. We included only primary studies of patients with COVID-19. Two reviewers screened titles and abstracts, then performed full-text screening, both independently and in duplicate. We first identified the 5 journals with the greatest numbers of eligible publications, then extracted data pertaining to the general characteristics, study population attributes, and research features of papers published in these journals.

RESULTS

Our analysis encompassed 142 primary studies. Of these, approximately 41.0% reported a funding source, while 3.5% disclosed a conflict of interest. In 2020, 42.9% of studies included fewer than 10 participants; however, by 2022, the proportion of studies with over 200 participants had increased to 40.6%. The most common design was the cohort study (48.6%), followed by case reports/series (35.2%). Only 3 randomized controlled trials were identified. Studies most frequently focused on prognosis (58.5%), followed by therapy/intervention (20.4%). Regarding the type of intervention/exposure, therapeutic clinical interventions comprised 26.1%, while studies of morbidity accounted for 13.4%. As for the outcomes measured, 50.7% of studies assessed symptoms/clinical status/improvement, and 14.1% evaluated mortality.

CONCLUSIONS

Employing a systematic approach, we examined the characteristics of research involving patients with COVID-19 that was published in Korean medical journals from 2020 onward. Subsequent research should assess not only publication trends over a longer timeframe but also the quality of evidence provided.

Pediatric humoral immune responses and infection risk after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and two-dose vaccination during SARS-CoV-2 omicron BA.5 and BN.1 variants predominance in South Korea

Background

Humoral immune responses and infection risk after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and coronavirus disease 2019 (COVID-19) vaccination during the Omicron BA.5 and BN.1 variants predominant period remains unexplored in pediatric population.

Methods

We examined anti-spike (anti-S) immunoglobulin G (IgG) responses in a total of 986 children aged 4-18 years who visited outpatient clinics between June 2022 and January 2023, with a history of SARS-CoV-2 infection alone, completed two doses of COVID-19 vaccination alone, vaccine-breakthrough infection (i.e., infection after the single dose of vaccination), and no antigenic exposure. Furthermore, to determine SARS-CoV-2 infection risk, the incidence of newly developed SARS-CoV-2 infection was investigated up to March 2023.

Results

The anti-S IgG levels in the 'vaccine-breakthrough infection' group exceeded those in the 'infection alone' and 'vaccination alone' groups (both P <0.01). Furthermore, the 'vaccination alone' group experienced more rapid anti-S IgG waning than the 'infection alone' and 'vaccine-breakthrough infection' groups (both P <0.01). We could not identify newly developed SARS-CoV-2 infection in the 'vaccine-breakthrough infection' group.

Conclusion

Our findings suggest that hybrid immunity, acquired from SARS-CoV-2 infection and COVID-19 vaccination, was a potentially higher and longer-lasting humoral immune response and protected against SARS-CoV-2 infection in pediatric population during Omicron BA.5 and BN.1 variants predominant.

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.

Evaluation of COVID-19 vaccine effectiveness in different high-risk facility types during a period of Delta variant dominance in the Republic of Korea: a cross-sectional study

BACKGROUND

We evaluated the effectiveness of coronavirus disease 2019 vaccination in high-risk facilities in the Republic of Korea during the period when the highly transmissible Delta variant was prevalent. Additionally, we aimed to explore any disparities in vaccine effectiveness (VE) across various types of institutions, specifically distinguishing between non-medical and medical establishments.

METHODS

We examined 8 outbreak clusters covering 243 cases and 895 contacts from 8 high-risk facilities divided into 2 groups: group A (4 non-medical institutions) and group B (4 medical institutions). These clusters were observed from July 27, 2021 to October 16, 2021 for the attack rate (AR) and VE with respect to disease severity. A generalized linear model with a binomial distribution was used to determine the odds ratio (OR) for disease severity and death.

RESULTS

AR was notably lower in group B (medical institutions). Furthermore, VE analysis revealed that group A exhibited higher effectivity for disease severity and death than group B. The OR for disease severity was 0.24 (95% confidence interval [CI], 0.03-2.16) for group A and 0.27 (95% CI, 0.12-0.64) for group B, with the OR for death at 0.12 (95% CI, 0.01-1.32) in group A and 0.34 (95% CI, 0.14-0.87) in group B.

CONCLUSION

Although VE may vary across institutions, our findings underscore the importance of implementing vaccinations in high-risk facilities. Customized vaccination programs, tailored response plans, and competent management personnel are essential for effectively addressing and mitigating public health challenges.

Mitigating from COVID-19 during Intercollegiate Sports Match

The coronavirus disease 2019 pandemic has posed a significant threat not only to health outcomes but also to other societal sectors, including the educational system. Apart from youth education, colleges and universities are characterized by the integration of in-depth theoretical and practical knowledge in young adulthood. Our observations in this study suggest that college fairs, sports matches, and extracurricular activities can be safely resumed when population-level immunity has reached herd protection.

Psychological and Personality Characteristics Associated With COVID-19 Vaccination Behavior in Korean General Population

BACKGROUND

This study characterized coronavirus disease 2019 (COVID-19) vaccination behavior in the Korean general population using cluster analysis and explored related psychological factors.

METHODS

We categorized 1,500 individuals based on their attitudes toward COVID-19 vaccination using hierarchical clustering and identified their level of vaccine acceptance. We examined the associations between vaccine acceptance and behavioral and psychological characteristics.

RESULTS

Clustering revealed three groups according to vaccine acceptance: 'totally accepting' (n = 354, 23.6%), 'somewhat accepting' (n = 523, 34.9%), and 'reluctant' (n = 623, 41.5%). Approximately 60% of all participants who belonged to the 'totally accepting' and 'somewhat accepting' groups were willing to receive a COVID-19 vaccine despite concerns about its side effects. High vaccine acceptance was associated with older age, regular influenza vaccination, and trust in formal sources of information. Participants with high vaccine acceptance had higher levels of gratitude, extraversion, agreeableness, and conscientiousness, and lower levels of depression, anxiety, and neuroticism.

CONCLUSIONS

People weighed the benefits of COVID-19 vaccination against the risk of side effects when deciding to receive the COVID-19 vaccine. Our findings also indicate that this vaccination behavior may be affected by coping mechanisms and psychological factors.

Effectiveness of Paxlovid, an Oral Antiviral Drug, Against the Omicron BA.5 Variant in Korea: Severe Progression and Death Between July and November 2022

BACKGROUND

Paxlovid is an oral antiviral drug that received emergency use authorization in South Korea for the treatment of patients with mild-to-moderate coronavirus disease 2019 (COVID-19) on January 14, 2022. Since the onset of the severe acute respiratory syndrome coronavirus 2 pandemic, the virus has continued to evolve. The emergence of new variants has raised concerns about possible reductions in the effectiveness of vaccines and drugs. The effectiveness of Paxlovid in patients infected with the omicron variant and subvariants has not yet been determined. This study assessed the effectiveness of Paxlovid at reducing the risk of severe/critical illness or death and death in patients with mild-to-moderate COVID-19 caused by omicron subvariant BA.5.

METHODS

In this nationwide retrospective cohort study, data on 8,902,726 patients were collected from four sources (the Drug Utilization Review database, COVID-19 Patient Information Management System, confirmed patient information, and basic epidemiological investigation data) between July 1 and November 30, 2022. Multivariable logistic regression analysis was conducted, with adjustment for age, sex, severe acute respiratory syndrome coronavirus 2 immunity (vaccination), and comorbidities.

RESULTS

A total of 1,936,925 patients with COVID-19 were included in the analysis, including 420,996 patients treated with Paxlovid, and 1,515,959 patients not treated with Paxlovid. Paxlovid treatment in patients aged ≥ 60 years of age was associated with significantly reduced risk of severe/critical illness or death (46.0%), and death rate (32.5%), and its effectiveness was high, regardless of vaccination status.

CONCLUSION

Paxlovid is effective at reducing the risk of death due to COVID-19 in patients with omicron BA.5 infection, especially in older patients, regardless of vaccination status. This suggests that older patients with COVID-19-related symptoms should be administered Paxlovid, regardless of their vaccination status, to reduce severity and risk of death.

Effectiveness of regdanvimab treatment for SARS-CoV-2 delta variant, which exhibited decreased in vitro activity: a nationwide real-world multicenter cohort study

Background

Immune-evading severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants are emerging continuously. The clinical effectiveness of monoclonal antibody agents that exhibit decreased in vitro activity against SARS-CoV-2 variants needs to be elucidated.

Methods

A nationwide, multicenter, retrospective cohort study was designed to evaluate the effectiveness of regdanvimab, an anti-SARS-CoV-2 monoclonal antibody agent. Regdanvimab was prescribed in South Korea before and after the emergence of the delta variant, against which the in vitro activity of regdanvimab was decreased but present. Mild to moderate coronavirus 2019 (COVID-19) patients with risk factors for disease progression who were admitted within seven days of symptom onset were screened in four designated hospitals between December 2020 and September 2021. The primary outcomes, O₂ requirements and progression to severe disease within 21 days of admission, were compared between the regdanvimab and supportive care groups, with a subgroup analysis of delta variant-confirmed patients.

Results

A total of 2,214 mild to moderate COVID-19 patients were included, of whom 1,095 (49.5%) received regdanvimab treatment. In the analysis of the total cohort, significantly fewer patients in the regdanvimab group than the supportive care group required O₂ support (18.4% vs. 27.1%, P < 0.001) and progressed to severe disease (4.0% vs. 8.0%, P < 0.001). In the multivariable analysis, regdanvimab was significantly associated with a decreased risk for O₂ support (HR 0.677, 95% CI 0.561-0.816) and progression to severe disease (HR 0.489, 95% CI 0.337-0.709). Among the 939 delta-confirmed patients, O₂ support (21.5% vs. 23.5%, P = 0.526) and progression to severe disease (4.2% vs. 7.3%, P = 0.055) did not differ significantly between the regdanvimab and supportive care groups. In the multivariable analyses, regdanvimab treatment was not significantly associated with a decreased risk for O₂ support (HR 0.963, 95% CI 0.697-1.329) or progression to severe disease (HR 0.665, 95% CI 0.349-1.268) in delta-confirmed group.

Conclusions

Regdanvimab treatment effectively reduced progression to severe disease in the overall study population, but did not show significant effectiveness in the delta-confirmed patients. The effectiveness of dose increment of monoclonal antibody agents should be evaluated for variant strains exhibiting reduced susceptibility.

Eight-Month Follow-up After the Third Dose of BNT162b2 Vaccine in Healthcare Workers: The Question of a Fourth Dose

BACKGROUND

A fourth dose of vaccination is known to help reduce the severity and mortality rate of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The South Korean vaccination guidelines for the fourth dose do not include healthcare workers (HCWs) as priority candidates. We investigated the necessity of the fourth dose in South Korean HCWs based on an 8-month follow-up period after the third vaccination.

METHODS

Changes in the surrogate virus neutralization test (sVNT) inhibition (%) score were measured at one month, four months and eight months after the third vaccination. The sVNT values were analyzed between infected and uninfected groups, and their trajectories were compared.

RESULTS

A total of 43 HCWs were enrolled in this study. In total, 28 cases (65.1%) were confirmed to be infected with SARS-CoV-2 (presumed omicron variant), and all had mild symptoms. Meanwhile, 22 cases (78.6%) were infected within four months of the third dose (median, 97.5 days). Eight months after the third dose, the SARS-CoV-2 (presumed omicron variant)-infected group showed significantly higher sVNT inhibition than that in the uninfected group (91.3% vs. 30.7%; P < 0.001). The antibody response due to hybrid immunity, provided by a combination of infection and vaccination, was maintained at sufficient levels for more than four months.

CONCLUSION

For HCWs who had coronavirus disease 2019 infection after completing a third vaccination, a sufficient antibody response was maintained until eight months after the third dose. The recommendation of the fourth dose may not be prioritized in subjects with hybrid immunity.

Effects of Omicron Infection and Changes in Serum Antibody Response to Wild-Type, Delta, and Omicron After a Booster Dose With BNT163b2 Vaccine in Korean Healthcare Workers

BACKGROUND

Although the primary vaccine coverage rate for coronavirus disease 2019 (COVID-19) in South Korea has exceeded 80%, the coronavirus continues to spread, with reports of a rapid decline in vaccine effectiveness. South Korea is administering booster shots despite concerns about the effectiveness of the existing vaccine.

METHODS

Neutralizing antibody inhibition scores were evaluated in two cohorts after the booster dose. For the first cohort, neutralizing activity against the wild-type, delta, and omicron variants after the booster dose was evaluated. For the second cohort, we assessed the difference in neutralizing activity between the omicron infected and uninfected groups after booster vaccination. We also compared the effectiveness and adverse events (AEs) between homologous and heterologous booster doses for BNT162b2 or ChAdOx1 vaccines.

RESULTS

A total of 105 healthcare workers (HCWs) that were additionally vaccinated with BNT162b2 at Soonchunhyang University Bucheon Hospital were enrolled in this study. Significantly higher surrogate virus neutralization test (sVNT) inhibition (%) was observed for the wild-type and delta variants compared to sVNT (%) for the omicron after the booster dose (97%, 98% vs. 75%; P < 0.001). No significant difference in the neutralizing antibody inhibition score was found between variants in the BNT/BNT/BNT group (n = 48) and the ChA/ChA/BNT group (n = 57). Total AEs were not significantly different between the ChA/ChA/BNT group (85.96%) and the BNT/BNT group (95.83%; P = 0.11). In the second cohort with 58 HCWs, markedly higher sVNT inhibition to omicron was observed in the omicron-infected group (95.13%) compared to the uninfected group (mean of 48.44%; P < 0.001) after four months of the booster dose. In 41 HCWs (39.0%) infected with the omicron variant, no difference in immunogenicity, AEs, or effectiveness between homogeneous and heterogeneous boosters was observed.

CONCLUSION

Booster vaccination with BNT162b2 was significantly less effective for the neutralizing antibody responses to omicron variant compared to the wild-type or delta variant in healthy population. Humoral immunogenicity was sustained significantly high after 4 months of booster vaccine in the infected population after booster vaccination. Further studies are needed to understand the characteristics of immunogenicity in these populations.