SARS-CoV-2 vaccination not linked to menstrual disturbance, bleeding in postmenopause

Key take a ways :

• The highest bleeding risk was after the third vaccination in the 1 to 7 and 8 to 90 days windows.
• Postmenopausal bleeding risk suggested an increase after the third dose of BNT162b2 (23%) and mRNA-1273 (33%).

Study results demonstrated no associations between SARS-CoV-2 vaccination and hospital admission or visit for postmenopausal bleeding and no association with premenopausal menstrual disturbance or bleeding.

“In a nationwide cohort study in Sweden, we evaluated the risks of menstrual disturbance and bleeding after SARS-CoV-2 vaccination in women who were before or after menopause,” Rickard Ljung, MD, MPH, PhD, professor in the division of use and information at the Swedish Medical Products Agency, Uppsala, and the Institute of Environmental Medicine at Karolinska Institute, Stockholm, and colleagues wrote. “High-quality data from nationwide registers enabled use to evaluate the risk by vaccine product and vaccination dose number.”

In this nationwide, register-based cohort study, published in The BMJ, researchers included 2,946,448 Swedish women aged 12 to 74 years from inpatient and specialized outpatient care in Sweden from December 2020 to February 2022. Of these women, 1,634,294 were premenopausal and 1,561,429 were postmenopausal. Researchers assessed SARS-CoV-2 vaccinations by vaccine product and dose over 1 to 7 days and 8 to 90 days from vaccination date.

The primary outcome was health care contact including admission or visit to a hospital for menstrual disturbance or bleeding for premenopausal and postmenopausal women.

A total of 87.6% of women in the cohort received at least one SARS-CoV-2 vaccination dose, and 64% of vaccinated women received three doses before conclusion of follow-up. Researchers observed the highest risks for bleeding in postmenopausal women after the third vaccination dose in the 1 to 7 days risk window (HR = 1.28; 95% CI, 1.01-1.62) and in the 8 to 90 days risk window (HR = 1.25; 95% CI, 1.04-1.5).

This risk for postmenopausal bleeding suggested an increased risk of 41% in the 1 to 7 days risk window and 23% in the 8 to 90 days risk window after receiving the third dose of BNT162b2 (Pfizer/BioNTech) and a 14% increased risk in the 8 to 90 days risk window after receiving the second dose. For mRNA-1273 (Moderna), researchers noted an increased risk of 33% after the third dose in the 8 to 90 days risk window. However, the association with ChAdOx1 nCoV-19 (Oxford-AstraZeneca) was less clear.

Researchers noted that any associations between vaccination and menstrual disturbance did not remain after adjustment for covariates.

“These findings do not provide any substantial support for a causal association between SARS-CoV-2 vaccination and health care contacts related to menstrual or bleeding disorders,” the researchers wrote.