Published: 17 November 2021

Safety Information

Monitoring communication

Patients should NOT decline vaccination subject to a monitoring communication. If you have any concerns with your vaccination, please contact your healthcare professional. A monitoring communication does not mean that the vaccine, medicine or medical device causes an adverse reaction.

Menstrual disorders and unexpected vaginal bleeding – Comirnaty (Pfizer COVID-19 vaccine)

17 November 2021

Monitoring ongoing.

Medsafe has been investigating a potential link between vaccination with Comirnaty and menstrual disorders or unexpected vaginal bleeding. As a result of our review we can reassure healthcare professionals and members of the public that no link has been found with vaccination.

The Centre for Adverse Reactions Monitoring (CARM) has received a number of reports of menstrual disorders or unexpected vaginal bleeding following vaccination with Comirnaty. Medsafe conducted a full review of the cases, as well as the international published literature, and post-marketing safety reports provided by the Sponsor (Pfizer). No evidence was found to suggest a link between vaccination with Comirnaty and menstrual disorders.

Additional information
Regulator actions

Additional information

Cases reported to CARM up to 7 October 2021 include 503 reports of heavy menstrual periods, early or unexpected menstrual periods, breakthrough bleeding, late or delayed menstrual periods, painful menstrual periods, and post-menopausal bleeding, in line with reporting seen in other countries. These case numbers are low when considering how commonly menstrual disorders normally occur, and the number of vaccines that have been administered.

Pfizer recently conducted an in-depth analysis of post-marketing safety data and found no safety signal for heavy menstrual bleeding or post-menopausal bleeding. Several international medicines regulatory bodies, including the Medicines and Healthcare products Regulatory Agency (MHRA, United Kingdom), the European Medicines Agency (EMA, European Union), and the Therapeutic Goods Administration (TGA, Australia) also conducted investigations and found no link between menstrual disorders or unexpected vaginal bleeding and Comirnaty vaccination. Similarly, in New Zealand, our review found no link.

Menstrual disorders and unexpected vaginal bleeding occur commonly in the population, irrespective of vaccination, and there are many possible underlying causes, including anxiety caused by the ongoing pandemic. Any changes occurring after COVID-19 vaccination are likely to be temporary, with no evidence that these temporary changes will impact future fertility.

Information about Comirnaty, including known side effects, can be found in the consumer medicine information (CMI) and data sheet.

Regulator actions

This issue was discussed with the COVID-19 Vaccine Independent Safety Monitoring Board (CV-ISMB) on 27 October 2021, who recommended Medsafe communicate their agreement with the conclusion that there is no evidence to support a link between menstrual disorders and Comirnaty administration.

Medsafe will continue to monitor the rate and pattern of occurrence of this issue.


Consumers and healthcare professionals are encouraged to report suspected adverse reactions to medicines to the Centre for Adverse Reactions Monitoring (CARM).

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