Background: Various adverse reactions have been reported after vaccination against COVID-19.

Objective: Few studies to date, however, have analyzed uterine bleeding after COVID-19 vaccination. The present study therefore evaluated the incidence of abnormal uterine bleeding after COVID-19 vaccination in South Korea.

Methods: Data on suspected adverse reactions to COVID-19 vaccination reported to the Korea Disease Control and Prevention Agency from February 26, 2021, to June 29, 2023 (week 121), were analyzed. Subjects who experienced abnormal uterine bleeding were identified, and the incidence of abnormal uterine bleeding was compared among the types of COVID-19 vaccines administered.

Results: . During the study period, 135,894,788 doses of COVID-19 vaccine were administered, with suspected adverse reactions occurring after administration of 483,391 doses (3.56 adverse reactions per 1,000 vaccinations) and abnormal uterine bleeding observed after administration of 6,288 doses (4.9 per 100,000 vaccinations).

Conclusions: Abnormal uterine bleeding was the fifteenth most common adverse reaction after COVID-19 vaccination. Studies are needed to clarify the causal relationships of vaccination and type of vaccine with abnormal uterine bleeding, as well as to develop protocols for the diagnosis and treatment of abnormal uterine bleeding after COVID-19 vaccination.

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