Coronavirus disease 2019 (COVID-19) has created major global challenges, with vaccination remaining the most effective measure to reduce severe outcomes and mortality. In Korea, six vaccines were approved, and the rapid rollout initiated in February 2021 contributed to comparatively low global mortality. As the epidemiological landscape of COVID-19 evolved and evidence on vaccine immunogenicity and safety accumulated, Korea adapted its vaccination strategies. During the 2024-2025 season, two mRNA vaccines (Pfizer-BioNTech and Moderna) and one recombinant protein vaccine (Novavax) targeting JN.1 lineage were administered primarily to high-risk groups. Beginning in October 2025, two mRNA vaccines (Pfizer-BioNTech and Moderna) adapted to LP.8.1 variant have been introduced as the updated 2025-2026 season formulations. Although safety concerns arose initially, Korean studies confirmed that COVID-19 vaccines provided strong effectiveness and acceptable safety, consistent with international findings. To enhance preparedness for future pandemics and epidemics, sustaining surveillance systems and maintaining updated vaccination policies are critical to ensure effective public health responses.

Background: Despite the recent introduction of a respiratory syncytial virus (RSV) vaccine, there is no sero-epidemiologic study of RSV infection among old adults in Korea. This study aimed to assess humoral immune responses to RSV among different age groups in Korea. Methods: A total of 400 serum samples (100 samples from each of the following age groups: 10-20, 21-40, 41-60, and 61-80 years) were selected randomly from a general population cohort used for health status evaluation in Korea (the Korea National Health and Nutrition Examination Survey 2019-2020 cohort). Anti-RSV IgM and IgG levels, along with total IgM and IgG levels, were measured in enzyme-linked immunosorbent assays. Results: Anti-RSV IgM levels were higher in individuals aged 10-20 and 21-40 years than in the other age groups (121.43 U/mL vs. 102.33 U/mL vs. 76.71 U/mL vs. 64.89 U/mL, P < 0.05), whereas anti-RSV IgG levels were similar across all age groups. Although the proportion of anti-RSV IgM relative to total IgM, respectively, was higher in the 10-20 age group than in the other groups (16.05% vs. 13.26% vs. 10.95% vs. 11.06%, P < 0.001), there was no significant difference among the 21-40, 41-60, and 61-80 age groups. Finally, there was no significant difference in anti-RSV IgG positivity rate among the age groups; however, the rate of anti-RSV IgM positivity was higher in the groups aged 10-20 and 21-40 years (73% vs. 54% vs. 28%vs. 28%, P < 0.001). Conclusion: RSV infections are recurrent in people over the age of 40 in Korea, but at a lower rate than in those aged 10-40. Therefore, more attention should be paid to RSV infections in the adult population in Korea.

Objectives People living with HIV (PLWH) are at increased risk for herpes zoster. This study aimed to evaluate and compare the immunogenicity and safety of the recombinant zoster vaccine (RZV) in PLWH across low and high CD4 counts, and in participants living without HIV (PLWoH). Methods In this non-randomized clinical trial, virologically suppressed PLWH receiving antiretroviral therapy and PLWoH received two doses of RZV. PLWH were stratified into low (<300 cells/μL) and high (≥300 cells/μL) CD4 groups. Anti-glycoprotein E (gE) antibody titers and gE-specific cell-mediated immunogenicity (CMI) were measured at baseline, 8 weeks post-dose one, and 4 weeks post-dose two. Vaccine response rates (VRRs), defined as a ≥4-fold antibody or ≥2-fold CMI increase, and reactogenicity were assessed. Results Sixty PLWH (30 low CD4, 30 high CD4) and 10 PLWoH (all male) were analyzed. Anti-gE titers increased significantly after each dose with no between-group differences. All groups achieved 100% humoral VRR after dose two, whereas CMI VRR differed significantly (33.3% low CD4, 50.0% high CD4, 80.0% PLWoH; P=0.041). Reactogenicity profiles were comparable. Conclusion RZV elicited robust humoral immunity in PLWH, regardless of the CD4 count; however, CMI was lower in PLWH than in HIV-negative individuals.

Bispecific antibodies (BsAbs) targeting CD3×CD20 have emerged as a promising immunotherapeutic approach in B-cell lymphoma. However, BsAbs have also led to concerns regarding infectious complications. Given the growing use of BsAbs in lymphoma, we aimed to investigate the incidence and risk factors for infections in patients with B-cell lymphoma receiving BsAb therapy. This single-center, longitudinal cohort study included B-cell lymphoma patients who received CD3×CD20 BsAb therapy between 2016 and 2024 at Seoul National University Hospital. Patients who received BsAb for less than 28 days were excluded. Clinical characteristics, including comorbidities, type of lymphoma, outcomes of BsAb therapy, and episodes of infection, were collected. A multivariate Fine and Gray model was performed to identify risk factors for infectious events. A total of 143 infection episodes were identified, of which 61.5% were grade ≥3. The most common sites of infection were lower respiratory tract (44.1%), followed by systemic infection (11.2%). The median time from BsAb initiation to the onset of all-grade infections was 6.5 months. Of the 122 patients, 74 (60.7%) experienced at least one infection episode, with 45 (36.9%) having grade ≥3 infections. The cumulative incidence of all-grade any infection and viral infection steadily increased over 24 months, reaching 75.6% (95% confidence interval [CI], 61.4–85.1) and 53.9% (95% CI, 41.1–65.1) at 24 months, respectively. Neutropenia (hazard ratio [HR], 6.94; 95% CI, 2.54–18.98) and hypogammaglobulinemia (HR, 3.41; 95% CI, 1.93–6.06) were associated with an increased risk of all-grade infection, while hypogammaglobulinemia was the sole independent risk factor for grade 3–5 infection (HR, 4.86; 95% CI, 2.50–9.43). Infections are common and clinically significant in patients with B-cell lymphoma receiving BsAb therapy, and the risk persists throughout the treatment course. To effectively mitigate infection risk, prophylactic measures against neutropenia and hypogammaglobulinemia should be implemented. All Authors: No reported disclosures

Identifying the causative pathogen is essential for selecting optimal antimicrobial therapy, and nanopore amplicon sequencing is an emerging approach for rapid nucleic acid based pathogen detection. This study reports clinical cases in which nanopore sequencing was used alongside conventional culture of clinical specimens obtained from infection sites, aiding clinical decision-making. From July 2024 to October 2025, eight patients with various infectious diseases were enrolled. All patients had at least one underlying disease, and their clinical diagnoses varied, including brain abscess, osteoarticular infection, pneumonia, and skin infection. Specimens, including abscess, ligament, intervertebral disc, joint fluid, sputum, and skin, were collected from infection sites for both routine culture and nanopore sequencing. Conventional cultures yielded no organisms in any of the clinical specimens. Nanopore sequencing was performed using the MinION device, and generated reads were analyzed through the EPI2ME platform. Nanopore amplicon sequencing identified pathogens in culture-negative infections, revealing fungi in three patients and bacteria in five. Targeted antimicrobial therapy based on sequencing led to clinical improvement in all cases. This case series demonstrates the potential utility of nanopore sequencing for detecting pathogens in culture-negative infections. Nanopore sequencing may inform treatment decisions when cultures are negative or are confounded by antibiotics.

ABSTRACT:Bispecific antibodies (BsAbs) have expanded therapeutic options for patients with relapsed/refractory B-cell lymphomas, yet their use has introduced a distinct spectrum of infectious complications that remain poorly characterized. In the largest cohort study to date, to our knowledge, we evaluated 109 patients treated with CD20×CD3 BsAbs between 2016 and 2024 to assess the incidence, characteristics, and risk factors of infections. Over a median follow-up of 28.4 months, 134 infectious episodes were identified, 61.2% of which were grade ≥3. The median time to infection onset was 6.6 months, with bacterial infections occurring earliest (5.9 months), followed by fungal (7.0 months) and viral infections (8.3 months). Among the microbiologically defined infections, viral infections were the most common (61.1%), with severe acute respiratory syndrome coronavirus 2 and cytomegalovirus (CMV) being the leading causes. Of the 109 patients, 68 (62.4%) experienced at least 1 infectious episode and 41 (37.6%) had grade ≥3 infections. The cumulative incidence of infection steadily increased over 24 months, reaching 76.4% at 24 months. The cumulative incidence of CMV infection steadily increased over the first 12 months. Neutropenia (absolute neutrophil count <1.0 × 109/L) and hypogammaglobulinemia (immunoglobulin G level <400 mg/dL) were independent risk factors for all-grade infection, whereas hypogammaglobulinemia was the sole independent risk factor for grade 3 to 5 infection. Early corticosteroid use was not associated with an increased infection risk. In summary, this study provides a temporal map of infection dynamics and highlights underrecognized complications, such as CMV reactivation. Risk-adapted therapeutic approaches and refined supportive care strategies are warranted for patients with B-cell lymphomas treated with BsAbs.

ABSTRACT Panton – Valentine leukocidin (PVL) is a leukocyte-lytic toxin produced by Staphylococcus aureus , which is primarily associated with skin and soft tissue infections. Notably, there has been an increase in the number of cases caused by the USA300 lineage in Japan. However, the reported prevalence of USA300 is limited in other Asian countries, including Korea. This study investigated the prevalence of PVL-positive methicillin-resistant S. aureus (MRSA) in Korea and Japan and compared their molecular epidemiological characteristics. A total of 463 MRSA strains were analyzed, comprising 283 strains from patients visiting two hospitals in Seongnam and Seoul, Korea, and 180 strains from six hospitals in Tokyo, Japan, between 2018 and 2019. The PVL-encoding genes lukS/F-PV were detected using PCR. Molecular epidemiological and phylogenetic analyses were performed using next-generation sequencing. Overall, 27 (9.5%) PVL-positive MRSA strains were detected among strains isolated from Korea, and 16 (8.9%) were detected among those isolated from Japan. Genotyping of PVL-positive strains revealed that 85.2% of Korean and 81.3% of Japanese strains belonged to USA300. Most USA300 strains from Japan and Korea formed distinct clusters in phylogenetic analyses. Meanwhile, ΨUSA300 and ST22-PT, clones that are prevalent in Japan, were isolated in Korea. This study showed that USA300 strains, which are becoming more prevalent in Japan, are also present in Korea. Furthermore, this study suggests that ΨUSA300 and ST22-PT may be spreading between these two countries. Therefore, it is necessary to continue monitoring the epidemiological trends of PVL-positive MRSA clones both domestically and internationally. IMPORTANCE Panton–Valentine leukocidin (PVL) is a major toxin produced by Staphylococcus aureus . Although a rapid increase in PVL-positive strains has been reported in Japan, data on PVL-positive strains in Korea remain limited. In this study, we performed a comparative analysis of PVL-positive S. aureus isolates from Korea and Japan. The results showed that the clinical backgrounds and genetic profiles of PVL-positive strains isolated in Korea and Japan were highly similar. Furthermore, we confirmed for the first time that clones circulating in Japan, including ΨUSA300 and ST22-PT, were also isolated in Korea. These findings provide valuable insights into the epidemiological status of PVL-positive S. aureus in East Asia.

OBJECTIVES:Persistent symptoms after SARS-CoV-2 infection (PASC, long COVID) remain a major public-health concern. We developed a data-driven definition and static and dynamic PASC scoring systems in a multicenter, prospective-retrospective observational cohort across 12 South Korean institutions. METHODS:Adults enrolled December 2022-March 2025 were followed up to 24 months; 8761 were recruited (7208 infected; 1553 controls) and 4668 met analysis criteria (4388 infected; 280 controls). Using participant-reported symptoms, surveys, and laboratory data, we identified nine symptoms robustly associated with PASC, with anosmia/ageusia and fatigue most influential. RESULTS:A static score integrating indicators observed within 24 months yielded an optimal threshold of 13, classifying 19% of infected participants and 4% of controls as PASC positive. A dynamic score tracking six-month intervals showed symptom burdens peaking at 0-5 months post-infection and declining thereafter; at the same threshold, 33% of infected participants were classified as PASC positive, reflecting temporal fluctuation. CONCLUSION:These data establish a quantitative definition of PASC and introduce a dynamic scoring framework to identify and monitor PASC, supporting future clinical research and practice.

The 20-valent pneumococcal conjugate vaccine (PCV20) was approved by the Korean Ministry of Food and Drug Safety in October 2024. Despite the ongoing national immunization programs that include pneumococcal conjugate vaccines for children and 23-valent pneumococcal polysaccharide vaccine (PPSV23) for adults, the burden of invasive pneumococcal disease and pneumococcal community-acquired pneumonia remains high among the elderly and high-risk adults. Serotypes 3 and 19A, both included in 13-valent pneumococcal conjugate vaccine (PCV13), continue to be the most prevalent serotypes, and infections caused by non-PCV13 serotypes have increased. Given the need to broaden serotype coverage and simplify vaccination strategies, the Korean Society of Infectious Diseases recommends either a single dose of PCV20 or sequential vaccination with 15-valent pneumococcal conjugate vaccine followed by PPSV23 for adults aged 65 years and older, and for high-risk adults aged 19-64 years. These recommendations are based on immunogenicity, safety, and cost-effectiveness data from recent clinical trials. Vaccine selection, dosing intervals, and schedules should be determined according to individual underlying medical conditions and previous vaccination history to optimize protection against pneumococcal disease in the adult population.

Abstract Background Viridans group streptococci (VGS) persist as the dominant cause of community-acquired native-valve endocarditis, contributing to 20% of cases. The incidence of streptococcal infective endocarditis (IE) exceeds that of Staphylococcus aureus IE, notably in Asia. However, the risk factors that guide the decision to conduct echocardiography to rule out IE in patients with VGS bloodstream infections (BSIs) remain unclear. Therefore, our study aimed to identify independent risk factors for IE in patients with VGS BSIs. Methods This retrospective study conducted at Seoul National University Hospital from January 2013 to December 2022 involved patients with VGS and nutritionally variant streptococcal BSIs, excluding single positive blood cultures and polymicrobial BSI cases. Independent risk factors were identified by multivariate logistic regression and sensitivity analyses according to echocardiography results, VGS species, or the inclusion of possible IE cases. Proportions of infective endocarditis by viridans group streptococci species. VGS species belonging to the mitis group are represented by the orange-coloured dots, and those in the non-mitis group are represented by the green-coloured dots. Circle size correlates with the number of IE cases attributed to each VGS species. Results Of 845 VGS BSI cases, 349 were analyzed and 86 IE cases were identified (24.6%). In the multivariate analysis, heart valve disease (adjusted odds ratio [aOR], 14.14, 95% confidence interval [CI], 6.14–32.58; P < 0.001), persistent bacteremia (aOR, 5.12, 95% CI, 2.03–12.94; P = 0.001), age (per year, aOR, 0.98; 95% CI, 0.96–1.00; P = 0.015), solid cancer (aOR, 0.26, 95% CI, 0.13–0.53; P < 0.001), and hematologic malignancy (aOR, 0.04; 95% CI, 0.01–0.41; P = 0.006) were independently associated with IE. Sensitivity analyses yielded consistent results; also, infection by a member of the mitis group was independent risk factor for IE (aOR, 6.50; 95% CI, 2.87–14.68, P < 0.001). Conclusion Younger age, heart valve disease, persistent bacteremia, absence of underlying hematologic malignancy or solid cancer, and BSI by a member of the mitis group were the independent risk factors for IE in VGS BSI patients. In conclusion, regular echocardiographic evaluation could be prudently considered based on these clinicomicrobiological risk factors. Disclosures All Authors: No reported disclosures

The clinical significance of cytomegalovirus reactivation in the lower respiratory tract (LRT) of critically ill patients remains unclear. We aimed to investigate the association between cytomegalovirus reactivation detected in LRT and intensive care unit (ICU) prognosis. This study included critically ill patients admitted to a medical ICU at a tertiary referral center in South Korea between January 2021 and June 2023. Cytomegalovirus load in LRT samples collected via bronchoscopy was measured within 7 days of admission. Detection of cytomegalovirus DNA in LRT was defined as reactivation. Associations between cytomegalovirus reactivation and ICU, in-hospital, 30-day, and 90-day mortality were assessed using multivariable Fine-Gray model adjusted for major clinical factors. Of the 322 patients (median age 68 years, 66.8

Cytomegalovirus (CMV) infection remains a major contributor to CMV-related and hematologic adverse outcomes in hematopoietic stem cell transplantation (HSCT) recipients. While letermovir has improved CMV prophylaxis strategies in this population, the clinical implications of low-grade CMV DNAemia during letermovir prophylaxis remain uncertain. We retrospectively analyzed 255 HSCT recipients who received letermovir at a tertiary hospital in Korea. Patients were stratified into three groups based on the highest CMV DNAemia levels observed during letermovir prophylaxis: no DNAemia (n = 72), low-grade DNAemia (< 1000 IU/mL; n = 171), and high-grade DNAemia (≥ 1000 IU/mL; n = 12). The association between low-grade CMV DNAemia and clinical outcomes was assessed using a multivariate Cox proportional hazards model. Most low-grade DNAemia cases were transient and resolved without antiviral therapy. Compared to no DNAemia, low-grade CMV DNAemia was not associated with an increased risk of clinically significant CMV infection by Day 100 (p = 0.262) or Day 365 (p = 0.399). No significant associations were observed with engraftment failure (p = 0.098), disease relapse (p = 0.165), or all-cause mortality (p = 0.537). Our findings suggest that close monitoring may be sufficient for low-grade DNAemia under letermovir prophylaxis.

Abstract Background During the coronavirus disease 2019 (COVID-19) pandemic, we observed that patients received anti-CD20 therapy progressed to severe pneumonia and underwent persistent viral shedding. We aimed to identify the association between anti-CD20 therapy and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, as well as the outcomes of COVID-19. Methods Using claims data derived from the Korean National Health Insurance Service, we conducted a matched nationwide retrospective cohort study. We included individuals aged ≥ 20 years diagnosed with conditions for which anti-CD20 therapy could be considered from January 2020 to December 2021. We defined the exposure variable by prescribing rituximab (RTX) at least once according to the database. COVID-19-related outcomes included hospitalization for COVID-19, ICU admission, mechanical ventilation administration, and all-case death. Patients prescribed RTX and those not prescribed RTX were defined as RTX users and non-users, respectively. The RTX users and non-users were 1:10 propensity score matched using sex, age, insurance type, and comorbidities. Logistic regression analyses were used to estimate the association between RTX and SARS-CoV-2 infection, as well as COVID-19-related outcomes. Results After 1:10 propensity score matching, 932 RTX users and 8,361 RTX non-users were analyzed. The proportion of vaccinated individuals was significantly lower in RTX users than in RTX non-users (69.3% vs. 90.9%; P < 0.001). RTX use was associated with an increased risk of all-case death (adjusted odds ratio [aOR] 1.85, 95% confidence interval [CI] 1.39–2.46, P < 0.001). In the subgroup analysis for vaccinated individuals, the risk of SARS-CoV-2 infection was significantly greater for RTX users compared to non-users (aOR 2.48, 95% CI 1.02–6.04, P = 0.045), and RTX use was also associated with a significantly increased risk of hospitalization (aOR 3.79, 95% CI 1.28–11.23, P = 0.016) and all-case death (aOR 3.85, 95% CI 2.54–5.84, P < 0.001). Conclusion The use of RTX was associated with an increased risk of all-cause death in immunocompromised patients. Among vaccinated individuals, RTX users were at an increased risk of SARS-CoV-2 infection, as well as an increased risk for hospitalization of COVID-19 and all-cause death. Disclosures All Authors: No reported disclosures

Abstract Background Correctional and detention facilities face significant challenges in controlling the spread of highly infectious pathogens such as SARS-CoV-2 due to overcrowded conditions, inadequate ventilation, and shared facilities. Despite reports on COVID-19 outbreaks in various correctional settings worldwide, investigations into outbreaks in metropolitan high-rise prisons remain scarce, warranting detailed examination. Diagnosed cases of coronavirus diseases 2019 (COVID-19) in detention center (blue) and South Korea (yellow), January through March 2022 Methods The detention center, which covers an area of 41,658 mm2, can accommodate 2,070 individuals and housed 1,977 inmates and 674 correctional officers at the time of outbreak detection. The facility comprises five buildings, including one 10-story and four 12-story buildings, with 47 wards. Each building is connected with the following building through a common hallway located at the distal end of each building. Descriptive analyses were conducted on demographic characteristics, symptom onset dates, comorbidities, vaccination status, and exposure history of confirmed COVID-19 cases. Vaccine effectiveness was estimated using logistic regression models. Epidemic curve of SARS-CoV-2 case-patients by building and floor(vertical axis), South Korea, 2022 Results From January 25 to March 2, 2022, 492 people, including 474 (30.0%) of 1,977 incarcerated persons (cumulative attack rate of 24%) and 18 (2.7%) of 674 staff members at the detention center, were confirmed with SARS-CoV-2 infection. High-rise facility characteristics contributed to rapid transmission, with the index case identified on January 25, 2022. However, the implementation of physical distancing, decarceration, limiting movement, and conducting serial and mass testing, despite being complex and requiring substantial resources, effectively slowed the spread of the Omicron variant amidst persistent community transmission. Vaccine effectiveness against infection was estimated at 52.7% (95% confidence interval, 37.2% to 64.4%) for three doses. Characteristics of coronavirus disease 2019 case-patients in a detention center, South Korea, 2022 Conclusion The findings underscore the vulnerability of high-rise detention centers to COVID-19 outbreaks and emphasize the effectiveness of multi-layered interventions in curbing transmission. Swift and comprehensive measures are crucial for controlling outbreaks in high-density, enclosed settings, informing future pandemic response efforts and policy development. Disclosures All Authors: No reported disclosures

Echinococcosis, caused by the tapeworm Echinococcus, is rare in Korea and is primarily imported from endemic areas. We report a case of a 37-year-old Korean man with multiple large hepatic cysts, initially diagnosed as simple cysts at a local clinic in 2018. The patient had lived in Oman, an endemic area, for several months in 2016. Upon referral to a tertiary hospital in 2023, due to progressive cyst enlargement, liver magnetic resonance imaging revealed three large cysts with a water lily sign. Serum IgG against Echinococcus was positive by enzyme-linked immunosorbent assay. After diagnosis of echinococcosis, treatment with albendazole and puncture-aspiration-injection-reaspiration (PAIR) was performed. Microscopic and molecular analysis of cyst aspirates confirmed Echinococcus granulosus infection. Follow-up computed tomography demonstrated a reduction in cyst size, yet the emergence of a new right pleural effusion and consolidation in the left lower lobe of the lung necessitated the continuation of albendazole therapy. This case highlights the importance of thorough travel history, imaging findings, and the effectiveness of PAIR combined with albendazole in treating imported echinococcosis.

In response to global reforms emphasizing competency-based learning and integrated curricula, South Korea is transitioning from its traditional 2 + 4 medical education model to a 6-year continuous medical curriculum. This shift addresses challenges such as fragmented learning pathways and insufficient integration between foundational and clinical training, which have limited the development of professional competencies and holistic student engagement. However, empirical evidence on stakeholder perspectives regarding this transition remains limited. This study aimed to examine faculty and student views on the proposed reform to inform its implementation and contribute to broader discussions on medical education transformation. A mixed-method study was conducted at Seoul National University College of Medicine. Quantitative data were collected from an online survey completed by 142 faculty members and 133 medical students. Qualitative data were gathered from two focus group interviews with fifteen students from both pre-medical and clinical phases. Survey responses were analyzed using Welch’s t-tests, and thematic analysis was applied to focus group interview data. Quantitative analysis revealed significant differences between faculty and student perceptions of the proposed 6-year continuous medical curriculum. Faculty reported higher scores for perceived needs (M = 4.05 vs. 2.79, p < .001), continuity, motivation, and curriculum supplementation (all p < .01). Students expressed greater concerns about curriculum overcrowding, academic burden, reduced interdisciplinary learning, and stress (all p < .01), and prioritized vacation time (M = 4.39 vs. 3.82, p < .01), extracurricular support (M = 4.14 vs. 3.52, p < .01), and pass/fail grading (M = 4.09 vs. 3.36, p < .01). Faculty emphasized integration of spiral and repetitive curriculum (M = 3.55 vs. 3.49, p = .02) and new content such as data science and health systems science (all p < .01). Thematic analysis identified student expectations for early integration of clinical and foundational subjects, balanced workload, and structured support systems, alongside concerns about marginalization of the pre-medical phase and prolonged stress. The transition to a 6-year continuous medical curriculum requires a comprehensive approach that engages key stakeholders, particularly students. Balancing educational innovation with curriculum manageability and student well-being is essential. Participatory design, phased implementation, and robust support systems are needed to ensure sustainable and adaptive curriculum reform.

Annual influenza vaccination is strongly recommended for immunocompromised individuals, who are at a higher risk of severe infection. The Korean Society of Infectious Diseases has revised its influenza vaccination recommendations for solid organ transplant recipients, advocating for the use of highly immunogenic vaccines, such as high-dose inactivated influenza vaccines or MF59-adjuvanted inactivated influenza vaccines, to enhance vaccine efficacy. While further research is needed to extend these recommendations to other immunocompromised populations, these vaccines have demonstrated improved immunogenicity without compromising safety. Expanding vaccination guidelines to additional immunocompromised groups should be considered as more evidence emerges.

Background: Bispecific antibodies (BsAbs) are a new class ofimmunotherapeutic agents for patients with multiple myeloma (MM). Although this new class of drug is associated with good disease control, they are also associated with increased risk of infectious complications. Since endemic community-acquired and nosocomial infections vary across the globe, we conducted this study to report real-world data of infectious complications associated with BsAbs in Korean population. Methods: We retrospectively reviewed all MM patients who received BsAb therapy between January 2021 and January 2024 at Seoul National University Hospital. We identified 61 patients who underwent BsAb therapy at our center with median follow-up of 34 weeks (95% confidence interval, 25.85-55.85). Thirty-three patients (54%) received B-cell maturation antigen (BCMA)-targeting BsAb, and 30 (49%) received combination therapy. Results: Of the 61 patients, 39 (64%) had at least one episode of infection. A total of 69 infections affecting patient management occurred during the study period, 3% grade 1 infection, 8% grade 2, 72% grade 3, 8% grade 4 and 8% grade 5. The most common type of infection was lower respiratory tract infection (n = 32/69, 46%), followed by systemic infection (n = 21/69, 30%). Etiology wise, viral infections were most common (67%), followed by fungal infections (13%) and bacterial infections (10%). Among viral infections, cytomegalovirus (CMV) was most common. Patients treated with BCMA-targeting BsAb or combination therapy were associated with higher incidence of CMV reactivation and clinically significant CMV infection. Conclusion: Particular pattern of infectious complications including CMV infection was noted in Korean patients. Identifying and determining the nature of infectious disease dynamics is becoming increasingly important for optimal resource allocation and shaping healthcare policies. In this regard, our first-in-Asian population study holds its value.

The coronavirus disease (COVID-19) pandemic accelerated development of various vaccine platforms. Among them, mRNA vaccines played a crucial role in controlling the pandemic due to their swift development and efficacy against virus variants. Despite the success of these vaccines, recent studies highlight challenges in evaluating vaccine efficacy, especially in individuals with prior COVID-19 infection. Weakened neutralizing antibody responses after additional doses are observed in these populations, raising concerns about using neutralizing antibody titers as the sole immune correlate of protection. While neutralizing antibodies remain the primary endpoint in immunogenicity trials, they may not fully capture the immune response in populations with widespread prior infection or vaccination. This review explores reduced neutralizing antibody responses in previously infected individuals, and their impact on vaccine efficacy evaluation. It also offers recommendations for improving efficacy assessment, stressing incorporation of additional immune markers such as cell-mediated immunity to enable more comprehensive understanding of vaccine-induced immunity.