Postmenopausal Bleeding Risk after COVID-19 Vaccination: A Population-Based Self-Controlled Case Series Study

This study aimed to evaluate whether COVID-19 vaccination increases the risk of postmenopausal bleeding requiring hospital care.

We conducted a nationwide population-based study using the integrated database of the Korea Disease Control and Prevention Agency COVID-19 registry and the National Health Insurance Service claims data. Women aged 56 years or older who received their first COVID-19 vaccine dose before December 2021 and were newly diagnosed with postmenopausal bleeding during the observation period were included. A self-controlled case series design was applied to compare the incidence of postmenopausal bleeding during predefined risk periods (1-30 days after each vaccine dose) with that during baseline periods within the same individuals. Incidence rate ratios (IRRs) and 95% confidence intervals (CIs) were estimated using conditional Poisson regression models.

Among 8075792 women aged 56 years or older who received COVID-19 vaccination, 5716 were diagnosed with postmenopausal bleeding. There was no significant increase in the risk of postmenopausal bleeding within 30 days following vaccination (IRR 0.98, 95% CI 0.92-1.04). Results remained consistent in subgroup and sensitivity analyses across vaccine types, doses, and age groups.

COVID-19 vaccination was not associated with an increased risk of postmenopausal bleeding requiring hospital care. These findings provide reassuring evidence supporting the safety of COVID-19 vaccines in postmenopausal women with respect to bleeding risk.