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42% of Women Report Heavier Menstrual Bleeding After COVID Vaccines

In the largest study of its kind to date, 42% of women who were menstruating regularly reported breakthrough bleeding after receiving a COVID-19 vaccine. Study participants who did not normally menstruate — including women on long-acting contraceptives and post-menopausal women — also experienced unusual bleeding.

In the largest study of its kind to date, 42% of women who were menstruating regularly reported breakthrough bleeding after receiving a COVID-19 vaccine.

Study participants, who did not normally menstruate — including women on long-acting contraceptives and post-menopausal women — also experienced unusual bleeding.

Researchers in April 2021 launched the survey after thousands of women reported changes to their menstrual cycles and unusual bleeding after getting vaccinated.

The survey sample included 39,129 currently and formerly menstruating participants between the ages of 18 and 80 years old who were fully vaccinated with Pfizer-BioNTech, Moderna, Johnson & Johnson (J&J), Novavax or AstraZeneca vaccines and had not previously had COVID-19.