Cardiac arrhythmias following COVID-19 vaccination: insights from the U.S. vaccine adverse event reporting system (VAERS), December 2020-January 2025, United States.

Background: Although COVID-19 vaccines are highly effective in preventing infection and severe disease, their cardiovascular safety, particularly regarding arrhythmic risk, continues to raise concerns. Methods: A disproportionality analysis was conducted using the U.S. Vaccine Adverse Event Reporting System (VAERS) to evaluate arrhythmia-related AEs reported between December 2020 and January 2025. Adverse events (AEs) were identified using MedDRA Preferred Terms, and signal strength was assessed by Reporting Odds Ratio (ROR) and Proportional Reporting Ratio (PRR). Results: A total of 52,518 reports were identified, with a median onset interval of 1 day after vaccination. The most frequent AEs were tachycardia (40.5%) and atrial fibrillation (16.9%). Atrial flutter, extrasystoles, and atrioventricular block exhibited the strongest signals. Severe events primarily involved ventricular and conduction abnormalities, particularly among older adults and male individuals. Reports involving mRNA vaccines were predominantly characterized by tachyarrhythmia-related events, whereas findings for bradyarrhythmia- and conduction-related events after adenoviral vector vaccination should be interpreted cautiously. Conclusions: Cardiac arrhythmias following COVID-19 vaccination typically occurred within the early post-vaccination period and demonstrated clear platform- and population-specific differences. Although the overall risk is low, enhanced early monitoring and stratified pharmacovigilance are warranted to optimize vaccine safety.