Introduction: While several studies have reported some cases of experiencing polymyalgia rheumatica (PMR) following COVID-19 vaccination, studies using large databases are lacking to clarify the association.
Aims: To investigate the risk of PMR after the COVID-19 vaccination using self-controlled case series (SCCS) analysis.
Methods: To perform SCCS analysis, we used the National Health Insurance Database, linked with the COVID-19 registry from the Korea Disease Control Agency between February 2021 and August 2023. We identified adults aged 50 years or older who received at least one dose of vaccines and were diagnosed with PMR diagnosis within the observation period, defined as 240 days after the first dose of the vaccine. The risk window was defined as 28 days after COVID-19 vaccination, and the control window encompassed the remainder of the observation period excluding the risk window. Incidence rate ratios (IRRs) were estimated using conditional Poisson regression with 95% confidence intervals (CIs), stratified by dose and vaccine type. Sensitivity analyses were also conducted by varying risk windows and outcome definitions.
Results: Among 44,818,078 COVID-19 vaccine recipients, 376 patients were diagnosed with PMR during the study period. The analysis indicated that COVID-19 vaccination was not associated with an increased risk of PMR (IRR, 0.74; 95% CI, 0.59-0.94). Rather, the risk of PMR was slightly reduced after the first dose (0.52; 0.34-0.79), with no significant association with the second and third doses of COVID-19 vaccine (0.83; 0.59-1.16 for second dose, 0.77,0.48-1.25 for third dose). Subgroup and sensitivity analyses were also aligned with the main findings.
conclusion: In this study, there was no association with the increased risk of PMR following COVID-19 vaccination. While these findings support evidence for the safety of COVID-19 vaccines, interpretation of the decreased risk of PMR should be cautious, and further research is needed to confirm these findings.

Introduction: Analyzing adverse events (AEs) from COVID-19 vaccination by gender is crucial for identifying potential differences in incidence and severity.
Aims: To examine gender differences in the types of AEs reported for COVID-19 vaccines in the Korea Institute of Drug Safety and Risk Management's Korea Adverse Event Reporting System database (KIDS KAERS DB).
Methods: Using the KIDS KAERS DB (2307A0006) from 26 February 2021 to 31 December 2022, we analyzed AEs following COVID-19 vaccination. We categorized AEs into two levels according to the Medical Dictionary for Regulatory Activities (MedDRA): the primary System Organ Class (SOC) for broad categorization and the Preferred Term (PT) for detailed information on individual AEs. At the SOC and PT levels, we calculated the percentage of AEs reported by each gender and determined the female-to-male (F/M) ratio of these percentages, along with 95% confidence interval (CI).
Results: A total of 887,917 cases were reported, mostly in females (68.4%) and individuals aged 19 to 65 years (78.7%). At the SOC level, females exhibited significantly higher rates in three categories, with the highest F/M ratio in metabolism and nutrition disorders at 1.67 (95% CI: 1.32–2.12). Males had higher rates in nine categories, with the largest difference in cardiac disorders (F/M ratio: 0.44, 95% CI: 0.42–0.46). At the PT level, females reported higher rates in 27 categories, with the greatest disparity in oropharyngeal pain (F/M ratio: 3.0, 95% CI: 2.11–4.26). Males had higher rates in 37 categories, with the most significant difference in death (F/M ratio: 0.29, 95% CI: 0.26–0.33).
Discussion/Conclusion: Our findings reveal significant gender differences in AEs following COVID-19 vaccination, underscoring the need for gender-specific data in vaccine safety monitoring. Identifying AEs more likely reported by each gender helps healthcare providers better monitor and manage these events, improving patient outcomes and vaccination confidence.

Introduction:
During the COVID-19 vaccination programs, the need for near-real time vaccine active surveillance has increased to provide timely information for regulatory decision-making.

Aims:
To conduct sequential testing of potential adverse events following COVID-19 vaccination in the Korean population

Methods:
The population-based active surveillance study was conducted utilizing a linked database of COVID-19 registry and the national health insurance claims data. Subjects included individuals aged over 12 who received either monovalent or bivalent vaccines from February 2021 to March 2023. For three pre-specified outcomes (acute myocardial infarction, myocarditis, and anaphylaxis) and a negative control event (colonic diverticulitis), monthly sequential testing was performed within vaccinated individuals. Using a maximized sequential probability ratio test (MaxSPRT), the incidence of each outcome following COVID-19 vaccination was compared with historical background rates with adjustments for multiple testing and claims processing delay. All analyses were stratified by four age groups, vaccine platform, and dose.

Results:
Sequential analyses identified safety signals for myocarditis following ribonucleic acid vaccines in aged 12 to 64 (Range for relative risks [RRs]: 2.41–7.89) and protein subunit vaccines in aged group 40 to 64 (Range for RRs: 30.00–33.33), and for anaphylaxis following ribonucleic acid vaccines in aged over 18 (Range for RRs: 2.49–17.30) and non-replicating viral vector vaccines in aged over 18 (Range for RRs: 1.61–40.95). These results were consistent with sensitivity analyses reflecting monthly incidence rates. No safety signals were observed for acute myocardial infarction and colonic diverticulitis.

Discussion/Conclusion:
The sequential testing detected safety signals for myocarditis and anaphylaxis shortly after vaccination program, which were acknowledged by the Korea Disease Control and Prevention Agency as associated with COVID-19 vaccines. This method can be proposed to effectively detect safety signals requiring further causality assessment for a newly introduced vaccines in the future.

Introduction. The scarcity of studies on vaccine-induced thrombosis and thrombocytopenia syndrome (TTS) limits the comprehensive understanding of vaccine safety on a global scale.
Aims. Our study aimed to assess the global burden of vaccine-induced TTS, identify the vaccines most associated with it, and suggest clinical implications regarding vaccination.
Methods. This study employed the World Health Organization international pharmacovigilance database, extracting records of vaccine-induced immune thrombotic thrombocytopenia from 1967 to 2023 (total reports, n=131,255,418). Global reporting counts, reported odds ratios (ROR), and information components (IC) were calculated to identify the association between 19 vaccines and the occurrence of vaccine-induced TTS across 156 countries.
Results. We identified 24,233 cases (male, n=11,559 [47.7%]) of vaccine-induced TTS among 404,388 reports of all-cause TTS. There has been a significant increase in reports of vaccine-induced TTS events over time, with a noteworthy surge observed after 2020, attributed to cases of TTS associated with COVID-19 vaccines. MMR vaccines were associated with most TTS reports (ROR [95% CI], 2.87 [2.75-3.00]; IC [IC0.25], 1.51 [1.43]), followed by hepatitis B, rotavirus diarrhea, encephalitis, hepatitis A, Ad5-vectored COVID-19, pneumococcal, and typhoid vaccines.
Discussion. Concerning age and sex-specific risks, reports of vaccine-induced TTS were more associated with females and younger age groups. The age group between 12-17 years exhibited significant sex disproportion. Most of these adverse events had a short time to onset and the fatality rate was 2.20%, the highest rate observed in the age group over 65 years and the lowest in the age group between 0-11 years.

Introduction:
The rotavirus vaccine (RV), including RotaTeq and Rotarix, is routinely co-administered with vaccines in the National Immunization Program (NIP) supporting 17 species, but data on concomitant administration effectiveness is limited.
Aims:
To evaluate hospitalization risk for acute gastroenteritis following administration of the RV and NIP vaccine concomitantly versus solely.
Methods:
We performed a retrospective cohort study using a linked database from the Korea Disease Control and Prevention Agency and National Health Insurance Service. The study included infants who completed RV vaccination between June 1, 2016, and December 31, 2022. The index date was defined as the date of each RV dose administration. Concomitant vaccination was defined as receiving both RV and NIP vaccines on the same day, while sole vaccination referred to RV vaccination only. The acute gastroenteritis-related hospitalizations were identified using the ICD-10 code A00-A09 and monitored for 14 days from the index date. We employed 1:1 propensity score matching to compare sole and concomitant vaccination for each RV dose. Using a conditional Poisson regression model, we calculated the incidence rate ratio (IRR) and 95% confidence interval (CI) adjusted by sociodemographic variables and birth-related comorbidities.
Results:
Among 1,476,994 infants who fully received the RV, the most frequently co-administered NIP vaccine combination was 'DTaP-IPV/Hib + PCV13' in all doses. Except for the third dose of RotaTeq, there were no statistically significant differences in IRRs between concomitant and sole vaccinations (Rotateq dose 1: IRR=0.93(95% CI: 0.64-1.34), dose 2: IRR=1.18(95% CI: 0.79-1.77) / Rotarix dose 1: IRR=0.74(95%CI: 0.74-1.02), dose 2: IRR=0.72(95%CI: 0.52-1.02)). For the third dose of RotaTeq, concomitant vaccination showed a significantly lower risk than sole vaccination (IRR=0.56, 95% CI: 0.36-0.87).
Discussion/Conclusion:
Concomitant administration of RV and NIP vaccines was not associated with an increased risk of acute gastroenteritis. These results support the coadministration of RV and NIP vaccines.

Aim/Objective: Rotavirus (RV) is a major cause of severe gastroenteritis and hospitalization in children. In Japan, the oral vaccines Rotarix® and Rotateq® were introduced in November 2011 and became publicly funded in October 2020. Evaluating the impact of these vaccines in clinical practice is important; however, they have not been verified on a large scale.

Methods: This study conducted a descriptive epidemiological analysis using the JMDC claims database; the target population was approximately 3.8 million children under age 12 from 2005 to 2023. The outcome was the number of hospitalizations for gastroenteritis and RV enteritis cases per 1,000 persons per year in children. It compared three time periods: before, after, and after the initiation of public funding of RV vaccine. Intussusception was evaluated as a secondary outcome, and congenital heart disease served as a control. The secondary analysis was an interrupted time series analysis (ITS), examining changes in the monthly slope.

Results: Before the vaccine introduction, there were 8.0 hospitalizations per 1,000 for gastroenteritis and 2.2 for RV enteritis. These numbers dropped to 5.1 and 1.1 after vaccine introduction and to 3.1 and 0.2 after public funding began, indicating a 61% decrease in gastroenteritis and an 89% decrease in RV enteritis hospitalizations (p<0.001). The time series analysis showed a monthly reduction of 0.7% in hospitalizations post-vaccine introduction (p=0.006). There were no significant changes in intussusception (p=0.496) and congenital heart disease cases (p=0.262).

Discussion and conclusion: The analysis revealed a significant decrease in hospitalizations due to gastroenteritis by 61% and RV enteritis by 81% after introducing the vaccines. However, public funding coincided with the coronavirus disease 2019 (COVID-19) pandemic, complicating the evaluation of its direct effects. Continued observation is recommended to assess the long-term benefits of rotavirus vaccination.