TY - JOUR
T1 - COVID-19 vaccination and the risk of abnormal uterine bleeding
T2 - A nationwide self-controlled case series study
AU - Jeong, Na Young
AU - Cho, Si Hyun
AU - Lim, Eunsun
AU - Lee, Jung Ryeol
AU - Song, Jae Yen
AU - Park, Joong Shin
AU - Choi, Nam Kyong
N1 - Publisher Copyright:
© 2025 The Authors
PY - 2025/9/17
Y1 - 2025/9/17
N2 - Objective: To assess the association between COVID-19 vaccination and the risk of the abnormal uterine bleeding (AUB) specifically focusing on vaginal or uterine bleeding that requires hospital care in women. Methods: We used a nationwide database in the Republic of Korea that combined COVID-19 registry data, which contains information on COVID-19 vaccination, with the claims database of the National Health Insurance Service. We included women aged 16–64 who received their first vaccine dose and were newly diagnosed with AUB in inpatient or outpatient settings within 180 days after receiving the first dose. A population-based self-controlled case series analysis was used to estimate the incidence rate ratio (IRR) during the risk periods, including 1–14, 1–21, and 1–28 days after each vaccine dose, compared to the baseline period. The baseline period was defined as the period of 1–180 days following the first vaccine dose, excluding the periods that corresponds to the risk periods. To address the SCCS assumption violation from recurrent nature, only the first event during the observation period was considered. Results: Among 83,422 eligible patients, the risk of AUB requiring hospital care within 14 days following COVID-19 vaccination was slightly elevated compared to the baseline period (IRR 1.04, 95 % CI 1.02–1.06). The risk was notably higher after the first dose, regardless of the risk interval (14-day risk period: IRR 1.12, 95 % CI 1.09–1.15; 21-day risk period: IRR 1.08, 95 % CI 1.06–1.10; 28-day risk period: IRR 1.07, 95 % CI 1.05–1.09). No significant increase was observed after the second and third doses. Conclusion: This study found a modest increase in healthcare utilization for AUB after the first dose of COVID-19 vaccination. However, this trend diminished with subsequent doses, showing no significantly increased risk. These findings should be interpreted while considering factors that influence healthcare-seeking behavior for unexpected vaginal or uterine bleeding.
AB - Objective: To assess the association between COVID-19 vaccination and the risk of the abnormal uterine bleeding (AUB) specifically focusing on vaginal or uterine bleeding that requires hospital care in women. Methods: We used a nationwide database in the Republic of Korea that combined COVID-19 registry data, which contains information on COVID-19 vaccination, with the claims database of the National Health Insurance Service. We included women aged 16–64 who received their first vaccine dose and were newly diagnosed with AUB in inpatient or outpatient settings within 180 days after receiving the first dose. A population-based self-controlled case series analysis was used to estimate the incidence rate ratio (IRR) during the risk periods, including 1–14, 1–21, and 1–28 days after each vaccine dose, compared to the baseline period. The baseline period was defined as the period of 1–180 days following the first vaccine dose, excluding the periods that corresponds to the risk periods. To address the SCCS assumption violation from recurrent nature, only the first event during the observation period was considered. Results: Among 83,422 eligible patients, the risk of AUB requiring hospital care within 14 days following COVID-19 vaccination was slightly elevated compared to the baseline period (IRR 1.04, 95 % CI 1.02–1.06). The risk was notably higher after the first dose, regardless of the risk interval (14-day risk period: IRR 1.12, 95 % CI 1.09–1.15; 21-day risk period: IRR 1.08, 95 % CI 1.06–1.10; 28-day risk period: IRR 1.07, 95 % CI 1.05–1.09). No significant increase was observed after the second and third doses. Conclusion: This study found a modest increase in healthcare utilization for AUB after the first dose of COVID-19 vaccination. However, this trend diminished with subsequent doses, showing no significantly increased risk. These findings should be interpreted while considering factors that influence healthcare-seeking behavior for unexpected vaginal or uterine bleeding.
KW - Abnormal uterine bleeding
KW - COVID-19
KW - Safety
KW - Self-controlled case series design
KW - Vaccination
KW - Vaginal bleeding
UR - https://www.scopus.com/pages/publications/105013495816
U2 - 10.1016/j.vaccine.2025.127619
DO - 10.1016/j.vaccine.2025.127619
M3 - Article
C2 - 40818314
AN - SCOPUS:105013495816
SN - 0264-410X
VL - 63
JO - Vaccine
JF - Vaccine
M1 - 127619
ER -
