Vaccination In Korea Research Articles

Position Statement about Gender-Neutral HPV Vaccination in Korea.

Given the rising incidence of human papillomavirus (HPV)-related diseases, including cervical, penile, and oropharyngeal cancers, particularly among men, the implementation of comprehensive HPV vaccination strategies is necessary in South Korea. This position statement advocates the introduction of gender-neutral vaccination (GNV) in the country. It recommends the administration of the HPV vaccine to both men and women aged 9-26 years to prevent a broad spectrum of HPV-related conditions. Specifically, individuals aged 9-14 years are advised to receive two doses of the vaccine, whereas those aged 15-26 years are advised to receive three doses. The optimal age for vaccination is identified as 11-12 years old. Additionally, this statement recommends that women aged 27 years and older be vaccinated based on the discretion of healthcare providers. The introduction of GNV is essential to curb the spread of HPV and reduce the overall burden of HPV-related cancers, making it a critical public health initiative in Korea.

Nurses' vaccination acceptance and related factors in the initial stage of COVID-19 vaccination in Korea: a cross-sectional study

Nurses' vaccination acceptance and related factors in the initial stage of COVID-19 vaccination in Korea: a cross-sectional study

Assessment of malignant potential for HPV types 16, 52, and 58 in the uterine cervix within a Korean cohort

High-risk human papillomavirus (HR-HPV) is the primary carcinogen in uterine cervical carcinoma. While genotype-specific carcinogenic risks have been extensively studied in Western populations, data from Korean are sparse. This study evaluates the malignant potential of the three most prevalent HR-HPVs in Korea: HPV16, HPV52, and HPV58. We analyzed 230 patients who underwent cervical conization and had been tested for HPV within a year prior to the procedure, excluding those with multiple infections. This analysis was confined to patients with single HPV infections and assessed outcomes of CIN3+, which includes carcinoma in situ (CIN3) and invasive carcinoma. The incidence of invasive cervical cancer was 6.7% for HPV16, 1.7% for HPV52, and 2.0% for HPV58; however, these differences were not statistically significant (p = 0.187). The rate of CIN3+ for HPV16, HPV52, and HPV58 were 70.6%, 51.7%, and 58.8%, respectively. Despite the small sample size, which may limit the robustness of statistical analysis, the data suggest a higher observed risk with HPV16. These findings highlight the need for vigilant clinical management tailored to specific HPV genotypes and support the implementation of a nine-valent vaccine in Korea. Physicians should be aware of these genotype-specific risks when treating patients.

Effectiveness of COVID-19 XBB.1.5 monovalent mRNA vaccine in Korea: interim analysis.

As coronavirus disease-2019 (COVID-19) becomes an endemic disease, the virus continues to evolve and become immunologically distinct from previous strains. Immune imprinting has raised concerns about bivalent mRNA vaccines containing both ancestral virus and Omicron variant. To increase efficacy against the predominant strains as of the second half of 2023, the updated vaccine formulation contained only the mRNA of XBB.1.5 sublineage. We conducted a multicenter, test-negative, case-control study to estimate XBB.1.5 monovalent vaccine effectiveness (VE) and present the results of an interim analysis with data collected in November 2023. Patients who underwent COVID-19 testing at eight university hospitals were included and matched based on age (19-49, 50-64, and ≥65 years) and sex in a 1:1 ratio. VE was calculated using the adjusted odds ratio derived from multivariable logistic regression. Of the 992 patients included, 49 (5.3%) received the XBB.1.5 monovalent vaccine at least 7 days before COVID-19 testing. Patients with COVID-19 (cases) were less likely to have received the XBB.1.5 monovalent vaccine (case 3.5% vs. control 7.2%, p=0.019) and to have a history of COVID-19 within 6 months (2.2% vs. 4.6%, p=0.068). In contrast, patients with COVID-19 were more likely to be healthcare workers (8.2% vs. 3.0%, p=0.001) and to have chronic neurological diseases (16.7% vs. 11.9%, p=0.048). The adjusted VE of the XBB.1.5 monovalent mRNA vaccine was 56.8% (95% confidence interval: 18.7-77.9%). XBB.1.5 monovalent mRNA vaccine provided significant protection against COVID-19 in the first one to two months after vaccination.

Active Surveillance for Safety Monitoring of XBB.1.5-Containing COVID-19 mRNA Vaccines in Korea.

The emergence of the omicron variant and its sub-lineages has necessitated vaccine updates for coronavirus disease 2019. In September 2023, the U.S. Food and Drug Administration approved an updated BNT162b2 vaccine targeting the omicron XBB.1.5 variant, which was initiated in Korea in October 2024. This study demonstrates the adverse events reported through active nationwide surveillance after XBB.1.5 vaccination in Korea. Since October 19, 2023, the Korea Disease Control and Prevention Agency has conducted daily Short Message Service surveys to collect data on health issues, fever, vaccination site reactions, systemic symptoms, impact on daily life, and healthcare visits. Among 20,180 respondents, 27.9% reported health issues. Adverse reactions peaked on day 1 (28.7%), including pain at the vaccination site, muscle pain, fatigue, and fever. These findings elucidate the short-term safety of the XBB.1.5 vaccine and support its co-administration with the influenza vaccine, reducing vaccine hesitancy and achieving herd immunity.

Risk of lymphadenopathy from SARS-CoV-2 vaccination in Korea: a self-controlled case series analysis.

To assess the risk of lymphadenopathy following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination. A self-controlled case series design was used to determine whether the risk of lymphadenopathy was higher in the 1-day to 42-day risk interval after coronavirus disease 2019 (COVID-19) vaccination compared to the control period. In addition, subgroup analyses were conducted according to baseline characteristics, time since vaccination, and sensitivity analyses adjusted for the length of the risk interval. The risk of developing lymphadenopathy in the risk interval (1-42 days) after COVID-19 vaccination compared to the control period was significantly increased, with a relative incidence (RI) of 1.17 (95% confidence interval [CI], 1.17 to 1.18) when the first, second, and third doses were combined. The RI was greater on the day of vaccination (1.47; 95% CI, 1.44 to 1.50). In subgroup analyses by baseline characteristics, a significantly increased risk or trend toward increased risk was observed in most subgroups except for those aged 70 years and older, with a significant increase in risk in younger individuals, those with a Charlson's comorbidity index <5, and those who received mRNA vaccines (mRNA-1273>BNT162b2). Within the 1-day to 42-day post-dose risk period, the relative risk was highest during the 1-day to 7-day post-dose period (1.59; 95% CI, 1.57 to 1.60) compared to the control period, and then the risk declined. In the sensitivity analysis, we found that the longer the risk window, the smaller the RI. SARS-CoV-2 vaccination is associated with a statistically significant increase in the risk of lymphadenopathy, and this risk was observed only with mRNA vaccines.

The serotype-specific prevalence of pneumococci in hospitalized pneumonia patients with COPD: a prospective, multi-center, cohort study.

The overall incidence of pneumococcal pneumonia is declining. However, the change in the pathogenic distribution of community-acquired pneumonia (CAP) in chronic obstructive pulmonary disease (COPD) patients and the serotype specificity of Streptococcus pneumoniae have not been evaluated in the post-era of pneumococcal vaccination in Korea. We conducted a prospective, multi-center, cohort study from seven University-affiliated hospitals. The primary objective was the identification of serotype-specific prevalence of pneumococcal pneumonia in COPD patients hospitalized for CAP. For the purpose, we conducted serotype-specific urine antigen detection (SS-UAD) assays for S. pneumoniae. The secondary objectives were other clinical characteristics of pneumonia including vaccination status. The total number of participants was 349. Most of them were male (95.1%) with old ages (75.55 ± 8.59 y). The positive rate for S. pneumoniae was 9.2% with SS-UAD assay and the common serotypes were 22F, 6A, and 6B. In the sputum, Pseudomonas aeruginosa (5.0%) and Haemophilus influenzae (4.0%) were common pathogens. The vaccination rate was 78.8%, 53.0%, and 25.8% for influenza, pneumococcal polysaccharide vaccine 23 (PPV 23), and pneumococcal protein- conjugated vaccine 13 (PCV 13), respectively. Thirteen patients died during hospitalization (mortality rate; 3.7%). There was no difference in the respective rate of influenza vaccination (79.2% vs. 69.2%, p = 0.288) and PCV 13 vaccination (25.6% vs. 30.8%, p = 0.443) between survivors and the deceased. Serotypes 22F, 6A, and 6B, which are covered either by PPV 23 or by PCV 13, are still common pneumococcal serotypes in COPD pneumonia in the post-vaccination era in Korea.

Parental intention to vaccinate daughters with the human papillomavirus vaccine in Korea: a nationwide cross-sectional survey.

We aimed to identify and compare the characteristics and factors associated with parental intention to vaccinate daughters under 12 years old against human papillomavirus (HPV), examining data from 2016 and 2020. Data were obtained from the Korean National Cancer Screening Survey conducted in 2016 and 2020. The present study included 3,510 parents with daughters under 12 years old. Changes in parental intention-to-vaccinate rates were calculated. To identify factors associated with parental intention to vaccinate their daughters, the chi-square test and logistic regression analysis were used. The percentage of respondents intending to vaccinate their daughters increased from 33.4% in 2016 to 58.9% in 2020, constituting a 25.5 percentage point (%p) increase. Since 2016, the proportion of men expressing positive intention towards HPV vaccination increased by 31.5%p, while that of women demonstrated a 20.9%p increase. Logistic regression analysis indicated that parents with a strong intention to vaccinate their daughters tended to be younger, more educated, and aware of the free vaccination program available, as well as to have a history of HPV vaccination and to have undergone cervical cancer screening within 2 years, compared to those who did not intend to vaccinate. Being a mother with a history of HPV vaccination was the strongest predictor of positive intention to vaccinate a daughter. The intention among parents to vaccinate daughters remains relatively low, although it is rising. To increase the HPV vaccination rate, strong recommendations and education should be provided to parents and the younger generation.

Safety surveillance of the NVX-CoV2373 COVID-19 vaccine among Koreans aged 18 years and over

BackgroundIn the Republic of Korea (Korea), the NVX-CoV2373 (Novavax) coronavirus disease 2019 (COVID-19) vaccination was administered to 18-year-olds and over from February 14, 2022. This study sought to assess the frequency and severity of reported adverse events following the Novavax COVID-19 vaccination in Korea. MethodsAdverse events based on two national vaccine safety data were analyzed; the COVID-19 vaccination management system (CVMS) and the text-message survey (TMS). ResultsCVMS identified that the reporting rate of adverse events per 100,000 doses were lower after booster doses (84.0) than after dose 1 (254.6) or dose 2 (272.9); and in 65-year-olds and over (83.4) than in 18- to 64-year-olds (168.1). The TMS found that local and systemic adverse events were lower in 65-year-olds and over than in 18- to 64-year-olds (p < 0.001). ConclusionsOverall, we identified no major safety issues and fewer adverse events following the Novavax COVID-19 vaccination among 65-year-olds and over in Korea.

Abstract TMP11: Cerebral Venous Sinus Thrombosis After Covid-19 Vaccination In Korea: A Nationwide Cohort Study

Introduction: Covid-19 vaccination is reported to relate with cerebral venous sinus thrombosis (CVST). This study aims to evaluate the association between CVST and Covid-19 vaccination in Korea. Methods: Hospitalized patients with incident CVST during January 2021 to January 2022 were extracted from nationwide health insurance claim data, and the history of vaccination was investigated. We used modified self-controlled case series (SCCS) analysis comparing the occurrence of CVST between risk period (within 28 days of covid-19 inoculation) and control period (excluding the risk period) and calculated the incidence rate ratio (IRR) for CVST in risk period compared to control period. Sensitivity analysis with extended risk period up to 5 weeks was also performed. Results: A total of 373 CVST cases were recruited in this SCCS study. The IRR for CVST in risk period was 1·41 (95% CI 1·01-1.95) compare with a control period. Subgroup analysis according to demographic profile revealed IRR of 1.86(1.01-3.42) and 2.53(1.40-4.58) in the age of 30-49 and 50-64 respectively, and also significantly higher IRR of 1.84(1.14-26.96) in women. CVST without thrombocytopenia group showed similar IRR of 1.45 (1.04-2.01). In the sensitivity analysis with risk period extended to 5 weeks, the IRR was 1.55 (1.13-2.13), which was not significantly different to 4 weeks risk period. Conclusions: A significant increase in the risk of cerebral venous thrombosis after COVID-19 vaccination is suggested from this study. The risk was higher in the old age and women. Because our data is health insurance claim data, the risk might be overestimated, and the validation of diagnostic accuracy is scheduled. Also nationwide registry of confirmed CVST cases will be presented and compared. Despite these limitation, this study heralds that CVST could follow after Covid-19 vaccination. Funding: This study was funded by research grant from Korean Center for Disease Conttrol, National Academy of Medicine in Korea, and Korean Stroke Society.

Integrated factors affecting intention of COVID-19 preventive behaviours including vaccination in Korea.

The aim of the study was to determine the multiple potential contributing factors in preventive behaviours, including COVID-19 vaccination for an effective campaign strategy. This is a descriptive correlation study to examine the effects of the behavioural outcome, attitude, subjective norm, perceived behavioural control, optimistic bias and social stigma on the intention of preventive behaviour, based on Ajen's Theory of Planned Behaviour. The survey was performed by a professional research company online from 16-19 July 2021. Two hundred and thirty-three participants who had not been vaccinated against COVID-19 at the time of data collection completed the survey. Perceived benefit, perceived behavioural control and social stigma are significantly associated with intention of preventive behaviours. The factors engaging in preventive behaviour presents us that our society is strongly influenced by social groups. Social groups influence decision-making in intention of preventing behaviour. Public education using social networks can increase such desirable behaviour.

Post-marketing surveillance study of the safety of the HPV-16/18 vaccine in Korea (2017–2021)

ABSTRACT Human papillomavirus (HPV) infection is associated with the risk of developing certain cancers, including cancers of the cervix, vulva, vagina, penis, anus, rectum, and oropharynx. In 2016, the bivalent HPV-16/18 vaccine was included in the Korea National Immunization Program. This vaccine protects against HPV types 16 and 18 and other oncogenic HPV types predominant in cervical and anal cancers. This post-marketing surveillance (PMS) study assessed the safety of the HPV-16/18 vaccine in Korea. The study was conducted in males and females aged between 9 and 25 years, from 2017 to 2021. Safety was measured in terms of frequency and intensity of adverse events (AEs), adverse drug reactions (ADRs), and serious adverse events (SAEs) after each vaccine dose. The safety analysis included all participants who were vaccinated as per prescribing information and who completed a 30-day follow-up after at least one dose. Data were collected using individual case report forms. The total safety cohort included 662 participants. A total of 220 AEs were reported in 144 subjects (21.75%), and there were 158 ADRs in 111 subjects (16.77%), with the most common being injection site pain in all cases. No SAEs or serious ADRs were reported. Most AEs were reported after the first dose and were injection site reactions with mild intensity that recovered. No individuals required hospitalization or an emergency department visit. Safety results showed that the HPV-16/18 vaccine was generally well tolerated in the Korean population, and no safety concerns were identified. ClinicalTrials.gov Identifier: NCT03671369.

Analysis of Antibody Responses After COVID-19 Vaccination in Liver Transplant Recipients: A Single-Center Study.

Liver transplant (LT) recipients were considered a vulnerable population during the coronavirus disease 2019 (COVID-19) pandemic. The clinical efficacy of the COVID-19 vaccine is unknown in immunocompromised patients. The purpose of this study was to provide evidence of antibody responses after COVID-19 vaccination in LT recipients. This study enrolled 46 patients who underwent LT at Samsung Medical Center (Seoul, Korea) before implementation of the one-dose vaccine in Korea. Those who completed the two-dose COVID-19 vaccine between August 2021 and September 2021 were included and followed through December 2021. Semiquantitative anti-spike serologic testing was performed using the Roche Elecsys anti-SARS-CoV-2 S enzyme immunoassay (Roche Diagnostics, Rotkereuz, Switzerland) with a positive cutoff of at least 0.8 U/mL. Among all 46 participants, 40 (87%) demonstrated an antibody response after the second dose of a COVID-19 vaccine, while six (13%) had no antibody response after the second dose. Upon univariate analysis, patients with higher antibody titer had longer years since LT (2.3 ± 2.8 vs. 9.4 ± 5.0, P < 0.001). A lower median tacrolimus (TAC) level before vaccination and after the second dose of COVID-19 vaccine indicated a significantly higher antibody response (2.3 [1.6-3.2] vs. 7.0 [3.7-7.8], P = 0.006, 2.5 [1.6-3.3] vs. 5.7 [4.2-7.2], P = 0.003). Period between 2nd vaccination and serologic testing was significantly higher in the antibody-response group compared to the no-antibody-response group (30.2 ± 24.0 vs. 65.9 ± 35.0, P = 0.012). A multivariate analysis of antibody responses revealed TAC level before vaccination as a statistically significant factor. A higher TAC level before vaccination resulted in less effective vaccination in LT patients. Booster vaccinations are required, especially for patients in the early stage after LT who have compromised immune function.

COVID-19 Vaccination in Korea.

Since December 2020, various coronavirus disease 2019 (COVID-19) vaccines have been developed and approved. As of February 2023, mRNA vaccines including bivalent vaccines (Pfizer/BioNTech, Moderna), recombinant protein vaccines (Novavax, SK Bioscience), and viral vector vaccines (AstraZeneca, Janssen) have been approved in Korea. COVID-19 vaccination can effectively reduce hospitalization and deaths due to symptomatic COVID-19, especially severe and critical COVID-19. The primary series vaccination against COVID-19 is recommended for all adults aged ≥18 years in Korea. Booster vaccination with the bivalent mRNA vaccine is available for those ≥12 years who have completed the primary series vaccination, regardless of the type of vaccine previously received, and is recommended for all adults. Booster vaccination can be administered since 90 days after the last dose. Localized and systemic adverse events following COVID-19 vaccination are relatively common and more frequently documented in younger age groups. Rare but potentially serious specialized adverse reactions include anaphylaxis, thrombosis with thrombocytopenia syndrome, myocarditis, and Guillain-Barré syndrome. Previous severe allergic reactions, such as anaphylaxis, to any COVID19 vaccine or vaccine component are considered a contraindication for vaccination. The indications and schedule for COVID-19 vaccination are subject to change based on further research results and the COVID-19 pandemic.

Self-reported adverse events after 2 doses of COVID-19 vaccine in Korea.

In Korea, a national coronavirus disease 2019 (COVID-19) vaccination program was implemented, including 4 vaccines against COVID-19. A text messaging-based survey, in addition to a passive adverse event reporting system, was launched to quickly report unusual symptoms post-vaccination. This study compared the frequency of adverse events after COVID-19 vaccination based on the vaccine type and the type of 2-dose regimen (homologous or heterologous). Self-reported adverse events were collected through a text-message survey for 7 days after each vaccination. This study included 50,950 vaccine recipients who responded to the survey at least once. Informed consent to receive surveys via text was obtained from the vaccine recipients on the date of first vaccination. The recipients of mRNA vaccines reported local and systemic reactions 1.6 times to 2.8 times more frequently after dose 2 than after dose 1 (p<0.001), whereas ChAdOx1-S recipients reported significantly fewer local and systemic reactions after dose 2 than after dose 1 (p<0.001). Local and systemic reactions were approximately 2 times and 4 times more frequent for heterologous vaccination than for BNT162b2/BNT162b2 and ChAdOx1-S/ChAdOx1-S regimens, respectively. Young individuals, female, and those receiving heterologous vaccine regimens including ChAdOx1-S/BNT162b2 vaccines reported more adverse events than older participants, male, and those with homologous vaccine regimens. Although a heterologous regimen, youth, and female sex were associated with a higher risk of adverse reactions after COVID-19 vaccination, no critical issues were noted. Active consideration of heterologous schedules based on the evidence of efficacy and safety appears desirable.

Influencing factor of COVID-19 vaccination trust and hesitancy in Wonju city, South Korea.

Social capital (SC) has been documented to effectively reduce the spread of diseases, including COVID-19; however, research pertaining to SC and COVID-19 vaccination in Korea is lacking. This cross-sectional study conducted in the city of Wonju, Gangwon Province, Korea (n = 1,096) examined the differences in COVID-19 vaccine trust and hesitancy considering individual characteristics and investigated the effects of SC on COVID-19 vaccine trust and hesitancy. SC was measured based on 14 items pertaining to social trust, network, and norms. Responses regarding COVID-19 screening history, vaccine trust, and vaccine hesitancy were also assessed. SC scores did not differ between sexes, but differed significantly according to age and household income; thus, adults aged 70-79 years had the highest SC scores, and mean SC score increased significantly with income. COVID-19 vaccine trust differed significantly according to age, average household income, social organization involvement, and SC score. COVID-19 vaccine hesitancy differed significantly with age, SC score, and COVID-19 screening history. In univariate logistic regression, age, average household income, social organization involvement, and SC score were significant predictors of vaccine trust; in multivariable analysis, however, the identified predictors were age and SC. In particular, people with an SC score ≥50 were 2.660 times more likely to trust COVID-19 vaccines than those with lower scores. In multivariable analysis, age and SC were significant predictors of vaccine hesitancy. In particular, people with an SC score ≥50 were 1.400 times more likely not to be hesitant about receiving COVID-19 vaccines than people with lower scores. These results indicate that prioritizing policies to increase SC and trust in the government could boost the COVID-19 vaccination rate.

한국 종두법의 발전과 의학 기술의 문제

In Korea, variolation (inoculation with Variola pus) and cowpox vaccine have been understood from the perspective of superiority and inferiority, but recently, the modernity and historical role of variolation are being re-examined. In addition, the role of Jeong Yak-yong(1762-1836), who introduced both variolation and cowpox vaccine, is also drawing attention in the process. However, the foundation for the spread of variolation and cowpox vaccine in Korea was very weak. This was due to a combination of several factors, including political repression against Western studies, and lack of medical knowledge networks as well as of public support and technology for securing and inoculating vaccine lymph. Among them, this article focuses on the importance of the original technology, which has been overlooked in the research on vaccination, such as the collection, storage, and inoculation technology involving vaccine lymph. Without vaccine lymph, vaccination is impossible. In the case of variolation, there was no difficulty in securing vaccine lymph as it was collected from a smallpox patient. However, in the case of cowpox vaccine, there was a problem of stability and technical difficulty in term of matured and freshly extracted vaccine lymph. In the case of cowpox vaccine, it was necessary to secure cowpox lymph, but until the first half of the 19th century, there was no way to secure cowpox lymph in Korea. It was impossible to produce on its own, and the cowpox lymph imported from abroad became rotten and thus ineffective. Unless vaccine lymph was secured, no matter how good the inoculation method was, it was useless. Variolation and cowpox vaccine were in a relationship of succession both theoretically and technologically. However, to be precise, what was used in cowpox vaccine was not Chinese-style, but Turkish-style(or Western-style) variolation. Whereas Chinese-style variolation was a method of blowing vaccine lymph into nostrils, Western-style variolation was a method of making an incision on the skin of the forearm and inoculating vaccine lymph in the incised area. Therefore, in order for the Chinese-style variolation to evolve to cowpox vaccine, it was necessary to explain and persuade why vaccine lymph should be inoculated and why the skin of the forearm should be incised. In Korea, the evolution of variolation to cowpox vaccine met a major obstacle due not only to political, social, and medical doubts but also to medical and technological factors such as the transmission of technology to secure and inoculate vaccine lymph.

Evaluation of the T cell and B cell response following the administration of COVID-19 vaccines in Korea.

BackgroundThe coronavirus disease (COVID-19) has been a worldwide concern since 2019. Vaccines are predicted to be crucial in preventing further outbreaks. The development and kinetics of immune responses determine the efficacy of COVID-19 vaccines.MethodsWe measured interferon-gamma (IFN-γ) levels upon administering homologous adenovirus vector-based (ChAdOx1-S [AZ], Ad26.COV2.S [JAN]), mRNA-based (BNT162b2 [PF]; mRNA-1273 [MO]), and heterologous (AZ/PF) vaccines in healthy Korean individuals using two IFN-γ release assays: the Covi-FERON ELISA and T-SPOT Discovery SARS-CoV-2 assay. B cell responses were evaluated by assessing the production of neutralizing antibodies by surrogate virus neutralization assay. The immune response among the vaccine groups was compared after adjusting the vaccination dose and interactions between each group.ResultsAZ triggered the highest T cell response after the first dose but showed instability after the second. PF and MO yielded stable and higher increments of T and B cell responses compared to AZ. MO yielded a higher immune response than PF. JAN yielded T and B cell responses at lower levels than the other vaccines. The booster dose triggered significant increases in the T and B cell responses and is therefore needed to protect against SARS-CoV-2 given the possibility of waning immune responses.ConclusionAdministering two doses of mRNA vaccines provides the most effective results among the administered vaccines in triggering the immune response specific to SARS-CoV-2 in healthy Korean individuals. Administration of booster doses demonstrated a significant increase in the immune response and may provide longer protection against SARS-CoV-2.

Neutralizing Activity Against SARS-CoV-2 Delta and Omicron Variants Following a Third BNT162b2 Booster Dose According to Three Homologous or Heterologous COVID-19 Vaccination Schedules.

With the emergence and rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta and Omicron variants, escaping vaccine-induced immunity is a concern. Three vaccination schedules, homologous or heterologous, have been initially applied due to an insufficient supply of vaccines in Korea. We investigated neutralizing activities against Omicron and Delta variants in each schedule. Three schedules using three doses of the BNT162b2 (BNT) or the ChAdOx1 (ChAd) vaccines include ChAd-ChAd-BNT, ChAd-BNT-BNT, and BNT-BNT-BNT. Neutralizing activities were evaluated using plaque-reduction neutralization test (PRNT) against wild type (WT) SARS-CoV-2, Delta variant, and Omicron variant. A total of 170 sera from 75 participants were tested, and the baseline characteristics of participants were not significantly different between groups. After the 2nd vaccine dose, geometric mean titers of PRNT ND50 against WT, Delta, and Omicron were highest after ChAd-BNT vaccination (2,463, 1,097, and 107) followed by BNT-BNT (2,364, 674, and 38) and ChAd-ChAd (449, 163, and 25). After the 3rd dose of BNT, the increase of PRNT ND50 against WT, Delta, and Omicron was most robust in ChAd-ChAd-BNT (4,632, 988, and 260), while the BNT-BNT-BNT group showed the most augmented neutralizing activity against Delta and Omicron variants (2,315 and 628). ChAd-BNT-BNT showed a slight increase of PRNT ND50 against WT, Delta, and Omicron (2,757, 1,279, and 230) compared to the 2nd dose. The results suggest that a 3rd BNT booster dose induced strengthened neutralizing activity against Delta and Omicron variants. The waning of cross-reactive neutralizing antibodies after the 3rd dose and the need for additional boosting should be further investigated.

Performance comparison between Elecsys Anti-SARS-CoV-2 and Anti-SARS-CoV-2 S and Atellica IM SARS-CoV-2 Total and SARS-CoV-2 IgG assays

Background: Although serological severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) tests from several manufacturers have been introduced in South Korea and some are commercially available, the performance of these test kits has not yet been sufficiently validated. Therefore, we compared the performance of Elecsys Anti-SARS-CoV-2 (ACOV2) and Anti-SARS-CoV-2 S (ACOV2S) and Atellica IM SARS-CoV-2 Total (COV2T) and SARS-CoV-2 IgG (sCOVG) serological tests in this study.Methods: A total of 186 patient samples were used. For each test, we analyzed the positive rate of serological antibody tests, precision, linearity, and agreement among the four assays.Results: The positive rates of COV2T, sCOVG, and ACOV2S were high (81.7%–89.2%) in total, with those for ACOV2S being the highest, while those of ACOV2 were as low as 44.6%. This may be related to the high completion rate of vaccination in Korea. The repeatability and within-laboratory coefficients of variation were within the claimed allowable imprecision; however, further research is needed to establish an allowable imprecision at low concentrations. COV2T showed a linear fit, whereas sCOVG and ACOV2S were appropriately modeled with a nonlinear fit. Good agreement was found among COV2T, sCOVG, and ACOV2S; however, the agreement between ACOV2 and any one of the other methods was poor.Conclusions: Considering the different antigens used in serological SARS-CoV-2 antibody assays, the performance of the tested assays is thought to show no significant difference for the qualitative detection of antibodies to SARS-CoV-2.