Correlation between the Cycle Threshold Values in Detection of Severe Fever with Thrombocytopenia Syndrome Virus Using PowerChekTM SFTSV Real-Time PCR Kit and Viral Load: Prognostic Implications.

BACKGROUND: This study aimed to analyze the correlation between the cycle threshold (Ct) values of severe fever with thrombocytopenia syndrome (SFTS) virus small (S) and middle (M) segments and the SFTS viral load, aiming to estimate the initial viral load and predict prognosis in the early clinical course. METHOD: A retrospective study was conducted with confirmed SFTS patients at Jeju National University Hospital (2016-2022). Patients were categorized into non-fatal and fatal groups. RESULTS: This study included 49 patients with confirmed SFTS (non-fatal group, n = 42; fatal group, n = 7). A significant negative correlation (-0.783) was observed between the log SFTS viral load and Ct values (p < 0.001). This negative correlation was notably stronger in the fatal group (correlation coefficient -0.940) than in the non-fatal group (correlation coefficient -0.345). CONCLUSION: In this study, we established a correlation between SFTS viral load and Ct values for estimating the initial viral load and early predicting prognosis. These results are expected to offer valuable insights for SFTS patient treatment and prognosis prediction.

Prevalence and Associated Factors of Depression and Anxiety Among Healthcare Workers During the Coronavirus Disease 2019 Pandemic: A Nationwide Study in Korea.

BACKGROUND: A healthcare system's collapse due to a pandemic, such as the coronavirus disease 2019 (COVID-19), can expose healthcare workers (HCWs) to various mental health problems. This study aimed to investigate the impact of the COVID-19 pandemic on the depression and anxiety of HCWs. METHODS: A nationwide questionnaire-based survey was conducted on HCWs who worked in healthcare facilities and public health centers in Korea in December 2020. Patient Health Questionnaire-9 (PHQ-9) and Generalized Anxiety Disorder-7 (GAD-7) were used to measure depression and anxiety. To investigate factors associated with depression and anxiety, stepwise multiple logistic regression analysis was performed. RESULTS: A total of 1,425 participating HCWs were included. The mean depression score (PHQ-9) of HCWs before and after COVID-19 increased from 2.37 to 5.39, and the mean anxiety score (GAD-7) increased from 1.41 to 3.41. The proportion of HCWs with moderate to severe depression (PHQ-9 ≥ 10) increased from 3.8% before COVID-19 to 19.5% after COVID-19, whereas that of HCWs with moderate to severe anxiety (GAD-7 ≥ 10) increased from 2.0% to 10.1%. In our study, insomnia, chronic fatigue symptoms and physical symptoms after COVID-19, anxiety score (GAD-7) after COVID-19, living alone, and exhaustion were positively correlated with depression. Furthermore, post-traumatic stress symptoms, stress score (Global Assessment of Recent Stress), depression score (PHQ-9) after COVID-19, and exhaustion were positively correlated with anxiety. CONCLUSION: In Korea, during the COVID-19 pandemic, HCWs commonly suffered from mental health problems, including depression and anxiety. Regularly checking the physical and mental health problems of HCWs during the COVID-19 pandemic is crucial, and social support and strategy are needed to reduce the heavy workload and psychological distress of HCWs.

Subdural Empyema from Streptococcus suis Infection, South Korea.

In Jeju Island, South Korea, a patient who consumed raw pig products had subdural empyema, which led to meningitis, sepsis, and status epilepticus. We identified Streptococcus suis from blood and the subdural empyema. This case illustrates the importance of considering dietary habits in similar clinical assessments to prevent misdiagnosis.

Identification and Antimicrobial Susceptibilities for Patients with Non-tuberculous Mycobacteria Infection in Jeju Island: Single-Center Retrospective Study.

BACKGROUND: The distribution of species and characteristics of non-tuberculous mycobacteria (NTM) differ, and surveillance data for changes in antimicrobial susceptibilities of NTM is insufficient. This study analyzed the changes in antimicrobial susceptibility trends across NTM species and assessed the appropriateness of empirical antimicrobial drugs for NTM. MATERIALS AND METHODS: We retrospectively analyzed the clinical characteristics, including demographics, distribution of NTM species, antimicrobial drug susceptibilities, and outcomes, at a teaching hospital in Jeju Island from 2009 - 2022. RESULTS: Overall, 342 patients were included in the analysis; 93.0% were classified into the pulmonary group (PG) and 7.0% into the extrapulmonary group (EPG). The isolation rate of Mycobacterium avium was significantly higher in PG (36.8% vs. 0%, P = 0.001), while that of Mycobacterium fortuitum was significantly higher in EPG (4.5% vs. 31.3%, P = 0.001). The antimicrobial susceptibility rate is higher against clarithromycin (89.9%) and amikacin (83.3%) and lower against rifampin (54.7%) and ethambutol (28.1%). The susceptibility rate to clarithromycin was over 80%, but those to rifampin and ethambutol showed decreasing annual trends. Of the 162 patients who received empirical antimicrobial therapy, actual antimicrobial susceptibility rates were high (90.1%) using empirical macrolide, and relatively low using ethambutol and rifampin (28.0% and 58.8%, respectively). CONCLUSION: This is the first study of analysis of the distribution, baseline characteristics, and antimicrobial susceptibility of isolated NTM species in pulmonary and extrapulmonary patients in Jeju Island over 10 years. Policies that continuously monitor changes in susceptibility rate are required to ensure effective treatment strategies.

Genome-informed investigation of the molecular evolution and genetic reassortment of severe fever with thrombocytopenia syndrome virus.

BACKGROUND: Severe fever with thrombocytopenia syndrome virus (SFTSV) is a viral pathogen causing significant clinical signs from mild fever with thrombocytopenia to severe hemorrhages. World Health Organization has paid special attention to the dramatic increase in human SFTS cases in China, Japan, and South Korea since the 2010s. The present study investigated the molecular evolution and genetic reassortment of SFTSVs using complete genomic sequences. METHODS/PRINCIPAL FINDING: We collected the complete genome sequences of SFTSVs globally isolated until 2019 (L segment, n = 307; M segment, n = 326; and S segment, n = 564) and evaluated the evolutionary profiles of SFTSVs based on phylogenetic and molecular selection pressure analyses. By employing a time-scaled Bayesian inference method, we found the geographical heterogeneity of dominant SFTSV genotypes in China, Japan, and South Korea around several centuries before and locally spread by tick-born spillover with infrequent long-distance transmission. Purifying selection predominated the molecular evolution of SFTSVs with limited gene reassortment and fixed substitution, but almost all three gene segments appeared to harbor at least one amino acid residue under positive selection. Specifically, the nonstructural protein and glycoprotein (Gn/Gc) genes were preferential selective targets, and the Gn region retained the highest number of positively selected residues. CONCLUSION/SIGNIFICANCE: Here, the large-scale genomic analyses of SFTSVs improved prior knowledge of how this virus emerged and evolved in China, Japan, and South Korea. Our results highlight the importance of SFTSV surveillance in both human and non-human reservoirs at the molecular level to fight against fatal human infection with the virus.

Epidemiologic and Clinical Characteristics of Patients with Severe Fever with Thrombocytopenia Syndrome at Tertiary Hospital in Jeju for 10 years.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS), which was first discovered in China in 2009, is an infectious disease with a high mortality rate, particularly in East Asia. This study aimed to investigate the epidemiological and clinical characteristics and risk factors for mortality by analyzing SFTS cases accumulated for up to ten years in Jeju, Korea. MATERIALS AND METHODS: Medical records of patients diagnosed with SFTS between March 2013 and August 2022 at a tertiary hospital in Jeju were analyzed retrospectively. We investigated data of patients with SFTS on the epidemiologic and clinical characteristics, laboratory findings, and administered treatments and compared the differences between fatal and non-fatal groups. RESULTS: We enrolled 91 SFTS-confirmed patients. The median age of patients was 62 years, and the fatality rate increased with age (P = 0.004). Fever was the most common symptom (84.6%), and diarrhea (37.4%) was also present in some cases. The overall fatality rate was 10.9%. Dyspnea (20.0% vs. 0.0%, P = 0.009) and changes in mental status (70.0% vs. 11.0%, P <0.001) were more frequent in fatal cases. Risk factor assessment revealed that a high aspartate aminotransferase /alanine aminotransferase ratio (odds ratio [OR]: 39.568, 95% confidence interval [CI]: 1.479 - 1,058.639, P = 0.028) and elevated total bilirubin levels (OR: 53.037, 95% CI: 1.064 - 2,643.142, P = 0.046) were also significantly associated with fatal cases. Plasma exchange (40.7%) was the most commonly administered treatment. CONCLUSION: SFTS has a high mortality rate; therefore, awareness of SFTS must be raised among physicians and citizens living in tick-inhabited areas, such as Jeju.

Fatal outcome of severe fever with thrombocytopenia syndrome (SFTS) and severe and critical COVID-19 is associated with the hyperproduction of IL-10 and IL-6 and the low production of TGF-ß.

Severe fever with thrombocytopenia syndrome virus (SFTSV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause the hyperproduction of inflammatory cytokines, which have pathological effects in patient including severe or fatal cytokine storms. To characterize the effect of SFTSV and SARS-CoV-2 infection on the production of cytokines in severe fever with thrombocytopenia syndrome (SFTS) and COVID-19 patients, we performed an analysis of cytokines in SFTS and COVID-19 patients and also investigated the role of interleukin-10 (IL-10) in vitro studies: lipopolysaccharide-induced THP-1-derived macrophages, SFTSV infection of THP-1 cells, and SARS-CoV-2 infection of THP-1 cells. In this study, we found that levels of both IL-10 and IL-6 were significantly elevated, the level of transforming growth factor-ß (TGF-ß) was significantly decreased and IL-10 was elevated earlier than IL-6 in severe and critical COVID-19 and fatal SFTS patients, and inhibition of IL-10 signaling decreased the production of IL-6 and elevated that of TGF-ß. Therefore, the hyperproduction of IL-10 and IL-6 and the low production of TGF-ß have been linked to cytokine storm-induced mortality in fatal SFTS and severe and critically ill COVID-19 patients and that IL-10 can play an important role in the host immune response to severe and critical SARS-CoV-2 and fatal SFTSV infection.

Carbapenem Use in the Last Days of Life: A Nationwide Korean Study.

The appropriate use of carbapenem is a critical concern for patient safety and public health, and is a national priority. We investigated the nationwide status of carbapenem prescription in patients within their last 14 days of life to guide judicious-use protocols from the previous study comprised of 1350 decedents. Carbapenem use was universally controlled through computerised authorisation system at all centres during the study period. Carbapenem prescribing patterns and their optimality were evaluated. A total of 1201 patients received antimicrobial agents within the last two weeks of their lives, of whom 533 (44.4%) received at least one carbapenem. The median carbapenem treatment duration was seven days. Of the 533 patients receiving carbapenems, 510 (95.7%) patients had microbiological samples drawn and 196 (36.8%) yielded carbapenem-resistant pathogens. A total of 200 (37.5%) patients were referred to infectious disease (ID) specialists. Of the 333 patients (62.5%) who did not have ID consultations, 194 (58.2%) were assessed as "not optimal", 79 (23.7%) required escalation, 100 (30.0%) required de-escalation, and 15 (4.5%) were discontinued. Notwithstanding the existing antibiotic restriction program system, carbapenems are commonly prescribed to patients in their last days of life.

Coinfection of Severe Fever With Thrombocytopenia Syndrome Virus and Coxiella burnetii in Developmental Stage of Hard Ticks in Subtropical Region of Korea.

BACKGROUND: Severe fever with thrombocytopenia syndrome virus (SFTSV) is transmitted through tick bites. Ticks are potential vectors for the bacterium Coxiella burnetii that causes Query fever. Here, we analyzed SFTSV and C. burnetii co-infection rates in ticks in rural areas of Jeju Island, South Korea. METHODS: Free ticks were collected from the natural environment of the island between 2016 and 2019, and SFTSV RNA was extracted. Additionally, ribosomal RNA gene sequencing was used to identify Coxiella species. RESULTS: Haemaphysalis longicornis was the most common tick species followed by H. flava. Tick number gradually increased from April, peaked in August, and was lowest in March. Of all the collected ticks, 82.6% (2,851/3,458) were nymphs, 17.9% (639/3,458) adults, and 0.1% (4/3,458) larvae. SFTSV-infected ticks comprised 12.6% of all ticks; their numbers were the lowest in November-December, increased from January, and were mostly identified in the adult stage during June-August. C. burnetii infections were detected in 4.4% of the SFTSV-infected H. longicornis ticks. C. burnetii co-infection was mainly observed in the nymph stage of H. longicornis, with the highest infection rate in January, followed by December and November. CONCLUSION: Our findings suggest that Jeju Island has a high SFTSV and potential C. burnetii infection in ticks. This study provides important insights regarding SFTS and Q fever risk to humans in South Korea.

Guidelines for Infection Control and Burnout Prevention in Healthcare Workers Responding to COVID-19.

During the coronavirus disease 2019 (COVID-19) pandemic, frontline healthcare workers (HCWs) suffered more distress from the possibility of contracting the virus, quarantine, social stigma, and prejudice against their families. Many studies have investigated the impact of the pandemic on HCWs; however, studies or guidelines presenting strategies to overcome these challenges are lacking. As part of a 2020 research project supported by the Ministry of Health and Welfare, titled "Health impact assessment of healthcare workers undertaking coronavirus disease 2019 treatment and management in Korea: Identifying problems and researching effective solutions" (HC20C0003), we created guidelines to respond to serious problems posed by infection control. and burnout among HCWs during COVID-19 response measures throughout the extended pandemic period. We formulated the guidelines by means of a systematic review and collated them with the latest literature. The guidelines will highlight the gravity and impact of infection control and burnout among HCWs responding to COVID-19 and include potential prevention strategies, and they can be used as a reference in the event of another emerging infectious disease outbreak in the future.

Use of Antibiotics Within the Last 14 Days of Life in Korean Patients: A Nationwide Study.

BACKGROUND: Antimicrobial prescriptions for serious chronic or acute illness nearing its end stages raise concerns about the potential for futile use, adverse events, increased multidrug-resistant organisms, and significant patient and social cost burdens. This study investigated the nationwide situation of how antibiotics are prescribed to patients during the last 14 days of life to guide future actions. METHODS: This nationwide multicenter retrospective cohort study was conducted at 13 hospitals in South Korea from November 1 to December 31, 2018. All decedents were included in the study. Antibiotic use during the last two weeks of their lives was investigated. RESULTS: A total of 1,201 (88.9%) patients received a median of two antimicrobial agents during the last two weeks of their lives. Carbapenems were prescribed to approximately half of the patients (44.4%) in the highest amount (301.2 days of therapy per 1,000 patient-days). Among the patients receiving antimicrobial agents, 63.6% were inappropriate and only 327 patients (27.2%) were referred by infectious disease specialists. The use of carbapenem (odds ratio [OR], 1.51; 95% confidence interval [CI], 1.13-2.03; P = 0.006), underlying cancer (OR, 1.56; 95% CI, 1.20-2.01, P = 0.047), underlying cerebrovascular disease (OR, 1.88; 95% CI, 1.23-2.89, P = 0.004), and no microbiological testing (OR, 1.79; 95% CI, 1.15-2.73; P = 0.010) were independent predictors for inappropriate antibiotic prescribing. CONCLUSION: A considerable number of antimicrobial agents are administered to patients with chronic or acute illnesses nearing their end-of-life, a high proportion of which are prescribed inappropriately. Consultation with an infectious disease specialist, in addition to an antimicrobial stewardship program, may be necessary to induce the optimal use of antibiotics.

Correlates of burnout among healthcare workers during the COVID-19 pandemic in South Korea.

Burnout is a form of negative emotional and physical response to job stress. This study aimed to investigate the prevalence of burnout among healthcare workers responding to the coronavirus disease 2019 (COVID-19) outbreak in Korea and to explore correlates of burnout among healthcare workers. A nationwide questionnaire-based survey was conducted from December 1, 2020, to January 29, 2021 on 1425 healthcare workers who worked in one of the 16 healthcare facilities designated for COVID-19 care, in public health centers, or as paramedics in Korea. Burnout was assessed using 16 Korean-adapted items based on the Oldenburg Burnout Inventory (OLBI). Data were collected using a structured questionnaire and analyzed using the R version 4.1.1 software program. OLBI results indicate clinically exhaustion in 84.5% (1204/1425) and clinically disengagement in 91.1% (1298/1425), and 77.3% (1102/1425) met the score criteria for both the exhaustion and disengagement subscales for burnout. Burnout rate was significantly increased in the group with chronic fatigue symptoms (Fatigue Severity Scale ≥ 3.22) after the outbreak of COVID-19 (OR, 3.94; 95% CI 2.80-5.56), in the female group (OR, 2.05; 95% CI 1.46-2.86), in the group with physical symptoms (Patient Health Questionnaire-15 ≥ 10) after the outbreak of COVID-19 (OR, 2.03; 95% CI 1.14-3.60), in the group with a higher Global Assessment of Recent Stress scale (OR, 1.71; 95% CI 1.46-2.01), in the group with post-traumatic stress symptoms (Primary Care Post-Traumatic Stress Disorder-5 ≥ 2) (OR, 1.47; 95% CI 1.08-2.01), and in the younger age group(OR, 1.45; 95% CI 1.22-1.72). The chronic fatigue symptoms were correlated with cumulative days of care (OR, 1.18; 95% CI 1.02-1.37). The physical symptoms were correlated with average contact hours with COVID-19 patients per day (OR, 1.34; 95% CI 1.17-1.54), and cumulative days of care (OR, 1.21; 95% CI 1.06-1.38). Most Korean healthcare workers suffered from burnout related to excessive workload during the COVID-19 pandemic. During a widespread health crisis like COVID-19, it is necessary to regularly check the burnout status in healthcare workers and reduce their excessive workload by supplementing the workforce and providing appropriate working hours sufficient rest hours.

The Evaluation of Surrogate Laboratory Parameters for Predicting the Trend of Viral Loads in Patients with Severe Fever with Thrombocytopenia Syndrome: Cross-Correlation Analysis of Time Series.

BACKGROUND: There is a correlation between the severe fever with thrombocytopenia syndrome (SFTS) viral load and disease severity; however, measurement of viral load is difficult in general laboratory and it takes time to obtain a viral load value. Here, the laboratory parameters for predicting the dynamic changes in SFTS viral load were identified. In addition, we tried to evaluate a specific time point for the early determination of clinical deterioration using dynamic change of laboratory parameters. MATERIALS AND METHODS: This observational study included SFTS patients in Korea (2013 - 2020). Cross-correlation analysis at lagged values was used to determine the temporal correlation between the SFTS viral loads and time-series variables. Fifty-eight SFTS patients were included in the non-severe group (NSG) and 11 in the severe group (SG). RESULTS: In the cross-sectional analyses, 10 parameters -white blood cell, absolute neutrophil cell, lymphocyte, platelet, activated partial thromboplastin time (aPTT), C-reactive protein, aspartate aminotransferase (AST), alanine transaminase (ALT), lactate dehydrogenase (LDH), and creatine phosphokinase (CPK)- were assessed within 30 days from the onset of symptoms; they exhibited three different correlation patterns: (1) positive, (2) positive with a time lag, and (3) negative. A prediction score system was developed for predicting SFTS fatality based on age and six laboratory variables -platelet, aPTT, AST, ALT, LDH, and CPK- in 5 days after the onset of symptoms; this scoring system had 87.5% sensitivity and 86.0% specificity (95% confidence interval: 0.831 - 1.00, P <0.001). CONCLUSION: Three types of correlation patterns between the dynamic changes in SFTS viral load and laboratory parameters were identified. The dynamic changes in the viral load could be predicted using the dynamic changes in these variables, which can be particularly helpful in clinical settings where viral load tests cannot be performed. Also, the proposed scoring system could provide timely treatment to critical patients by rapidly assessing their clinical course.

Serological Evidence of Severe Fever with Thrombocytopenia Syndrome Virus and IgM Positivity Were Identified in Healthy Residents in Vietnam.

Severe fever with thrombocytopenia syndrome (SFTS), an emerging tick-borne viral disease, is prevalent in East Asia and has also been reported in Southeast Asia since 2019. SFTS patients in Vietnam were first reported in 2019. However, the seroprevalence of severe fever with thrombocytopenia syndrome virus (SFTSV) in Vietnam has not been reported. To investigate the seroprevalence of SFTSV in Vietnam, we collected serum samples from 714 healthy residents in Thua Thien Hue and Quang Nam Province, Vietnam, and the seroprevalence of SFTSV was assessed using immunofluorescence antibody assay (IFA), Enzyme-Linked Immunosorbent Assays (ELISAs) and the 50% focus reduction neutralization test (FRNT50) assay. The seroprevalence of anti-SFTSV IgM or IgG was observed to be 3.64% (26/714), high IgM positivity was >80 (0.28%, 2/714) and the titer of neutralizing antibodies against SFTSV ranged from 15.5 to 55.9. In Pakistan, SFTSV infection confirmed using a microneutralization test (MNT) assay (prevalence is 2.5%) and ELISAs showed a high seroprevalence (46.7%) of SFTSV. Hence, the seroprevalence rate in Vietnam is similar to that in Pakistan and the number of SFTS patients could increase in Vietnam.

A CRISPR-Cas12a-based diagnostic method for multiple genotypes of severe fever with thrombocytopenia syndrome virus.

Severe fever with thrombocytopenia syndrome virus (SFTSV) infection is commonly reported in countries of Northeast Asia including China, Japan and South Korea. The majority of the SFTS patients are elderly and the average fatality rate is more than 10%. A rapid and sensitive diagnostic method to monitor and prevent SFTSV transmission remains an urgent clinical challenge. In this study, we developed a molecular diagnostic technique for detection of SFTSV using the CRISPR-Cas12a system combined with reverse transcription recombinase polymerase amplification (RT-RPA). Using this method, we successfully diagnosed SFTSV infections with the reaction time of 50 min from blood plasma without cross-reactivity to other viruses, supporting its application for rapid and sensitive diagnosis of SFTS.

Tocilizumab therapy for IL-6 increment in a patient with non-fatal severe fever with thrombocytopenia syndrome.

We report the administration of an anti-interleukin (IL)-6 antibody in a case of severe fever with thrombocytopenia syndrome (SFTS) with an increase in IL-6. On the day of admission, SFTS viral load and IL-6 concentration were 93 831 copies/ml and 5.4 pg/ml, respectively, and tocilizumab was administered. SFTS viral load decreased to 17 821.1 copies/ml on the 3rd day of admission, while IL-6 levels increased to 104.9 pg/ml; SFTS viral load and IL-6 levels had decreased to 2876.4 copies/ml and 48.2 pg/ml on 7th day of admission, respectively. The patient fully recovered no tocilizumab adverse events.

Expert Consensus on Measures to Promote Physical and Psychological Health among COVID-19-Related Healthcare Workers in Korea using Delphi Technique.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has caused health problems and distress among healthcare workers (HCWs), so supportive measures to promote their health and relieve distress are needed. MATERIALS AND METHODS: We conducted two rounds of Delphi surveys with 20 COVID-19-related frontline healthcare professionals and public officials. The surveys evaluated means of supporting HCWs' health by improving health care systems and working environments in terms of effectiveness and urgency. The validity of the measures was assessed by calculating the content validity ratio. RESULTS: The top-priority measures to support HCWs were "secure isolation units capable of treating severe cases" in the facility infrastructure category, "secure nursing staff dedicated for patients in the intensive care units" in the personnel infrastructure category, "improve communication between central office and frontline field" in the cooperation system category, "support personal protective equipment and infection control supplies" in the aid supplies category, and "realization of hazard pay" in the physical/mental health and compensation category. CONCLUSION: There was consensus among the experts on the validity and priorities of policies in the facility, personnel, cooperation, supplies, and compensation categories regarding measures to promote COVID-19 related HCWs' health.

Healthcare Workers in South Korea Maintain a SARS-CoV-2 Antibody Response Six Months After Receiving a Second Dose of the BNT162b2 mRNA Vaccine.

Background: Effective vaccines against coronavirus disease 2019 (COVID-19) are available worldwide; however, the longevity of vaccine effectiveness is not known. Objective: We performed a prospective observational study to assess the antibody response of healthcare workers against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) after BNT162b2 mRNA COVID-19 vaccination. Methods: SARS-CoV-2 neutralizing antibody (nAb) and spike (S) protein-IgG (S-IgG) antibody titers were examined in participants who received two doses of the BNT162b2 mRNA COVID-19 vaccine in a single center between March 1, 2021, and October 11, 2021. Antibody levels were analyzed at four times: before vaccination (visit 1), 4 weeks after the first vaccination (visit 2), 3 months after the second vaccination (visit 3), and 6 months after the second vaccination (visit 4). Results: A total of 249 healthcare workers at Jeju National University Hospital were enrolled in this study, and 982 blood samples were analyzed. The mean age was 38.1 ± 9.5 years, and 145 (58.2%) participants were females. Positive nAbs (inhibition rates ≥ 20%) were measured in 166/249 (66.7%) subjects at visit 2, 237/243 (97.5%) subjects at visit 3, and 150/237 (63.3%) subjects at visit 4. A S-IgG (≥50 AU/mL) positivity was detected in 246/249 (98.8%) subjects at visit 1, and all participants had positive S-IgG antibody levels at visits 3 and 4 after being fully vaccinated. Further analysis of S-IgG levels revealed a median quantitative antibody level of 1275.1 AU/mL (interquartile range [IQR] 755.5-2119.0) at visit 2, 2765.9 AU/mL (IQR 1809.8-4138.4) at visit 3, and 970.1 AU/mL (IQR 606.0-1495.9) at visit 4. Patient characteristics, such as age, body mass index, and comorbidity, had no relationship with nAb or S-IgG levels at any of the visits. Considering the change in antibody levels over time, both nAb and S-IgG levels at visit 4 decreased compared with the corresponding levels at visit 3. No evidence of SARS-CoV-2 infection was found among any of the participants throughout the study. Conclusions: The BNT162b2 mRNA vaccine was effective in protecting healthcare personnel working in COVID-19-related departments. While the level of S-IgG antibodies was maintained for 6 months after the second vaccination, nAb levels waned over this 6-month period, indicating the need for a booster vaccination in some healthcare workers 6 months after full vaccination. Herein, we suggest that further studies are needed to evaluate the need for an interval of booster vaccination after full vaccination.