No evidence that menstrual disorders are triggered by COVID-19 vaccination

24 September 2021

The Danish Medicines Agency and the European Medicines Agency have reviewed cases of menstrual disorders reported as side effects after COVID-19 vaccination and have found no causal association.

Menstrual disorders are common, especially in young women of child-bearing age and women who are nearing menopause. Menstrual disorders may be completely normal but can also be caused by an underlying condition such as endometrial abnormalities, coagulation disturbances, stress, infections, hormonal imbalances or cellular changes.

Side effect reports describing menstrual disorders were discussed at the latest meeting of the Pharmacovigilance Risk Assessment Committee, PRAC. The meeting assessed that no causal association could so far be established between the COVID-19 vaccines and menstrual disorders but maintained that the issue should still be monitored. 

The companies marketing the COVID-19 vaccines in the EU have been asked to provide further data as part of the monthly safety update reports that are included in the monitoring of vaccine safety. These safety updates can be found on the website of the Danish Medicines Agency under News.

As at 16 August 2021, the Danish Medicines Agency has received about 2800 reports describing menstrual disorders. The reports are distributed across all the COVID-19 vaccines authorised in the EU and across women of child-bearing age and postmenopausal women.

As at 17 August 2021, altogether 1,958,929 women have been fully vaccinated for COVID-19 in Denmark whereas 2,205,085 have received their first dose. The number of reports describing menstrual disorders considered low given the number of vaccinated women and given that menstrual disorders are rather common.

At the Danish Medicines Agency, we monitor the COVID-19 vaccines closely. Reports on suspected side effects are essential to our monitoring tasks because they can signal emerging new or changed risks that we need to investigate further.

Our monitoring activities did not find any signals suggesting that bleeding disturbances could be a new side effect. As part of our monitoring of the COVID-19 vaccines, we also carried out an additional review of a selection of the submitted reports, none of which led to the identification of signals suggestive of an association between the COVID-19 vaccines and bleeding disturbances.

These reports generally concerned spontaneous bleeding in most cases lasting from one to 14 days and requiring neither the advice of a doctor nor treatment. For most of the reported cases, other events could explain the irregular menstrual cycles. The Danish Medicines Agency has found no information pointing to a causal association between these menstrual cycle bleeding irregularities and COVID-19 vaccination.

The Danish Medicines Agency and the EMA will continue to monitor menstrual disorders reported as a side effect after COVID-19 vaccination and advise women who experience unexpected bleeding (e.g. in postmenopausal women) or who are concerned about prolonged or severe bleeding to consult a doctor.