Reporting rates of abnormal uterine bleeding after COVID-19 vaccination in South Korea.

Introduction: Abnormal uterine bleeding after COVID-19 vaccination has been reported, but few studies have characterized population-level reporting rates. We evaluated AUB reporting in South Korea. Methods: We analyzed suspected adverse reactions reported to the Korea Disease Control and Prevention Agency from 26 February 2021 to 29 June 2023 (week 121). Cases with AUB were identified, and reporting rates were compared across vaccine types and doses. Results: During the study period, 135,894,788 doses were administered, with 483,391 suspected adverse reactions (356 per 100,000) and 6,288 AUB reports (4.9 per 100,000). AUB ranked 15th among reported adverse events. Reporting rates varied by manufacturer and dose. Discussion: These descriptive pharmacovigilance findings do not estimate incidence or imply causality. Prospective, controlled studies are needed to clarify causal relationships and to inform diagnostic and management protocols for AUB after vaccination.