New Study of 9,500 Women Finds COVID-19 Jab Could Lead to Heavier Menstrual Bleeding

A nurse administers a COVID-19 vaccine booster to a person at a hospital in Hines, Ill., on April 1, 2022. Scott Olson/Getty Images

Women vaccinated for COVID-19 have a slightly higher risk of heavier menstrual bleeding, according to a new study.

According to the study that examined 7,401 vaccinated and 2,154 unvaccinated women, researchers found an increase in the amount of bleeding for 40 out of 1,000 individuals after one dose of the jab.

“Menstruation is a routine bodily function and a key indicator of overall health, so it’s crucial that we understand the scope of this issue among the global population,” said Dr. Alison Edelman, a physician-scientist from Oregon Health and Science University.

“The more we can understand about these reported changes, the more effectively we’re able to counsel individuals about what to expect with a COVID-19 vaccine and how to make an informed decision about getting vaccinated.”

Menstrual cycles are considered a ‘vital sign’ of overall health. Dreamstime/TNS

While there is growing research on the link between COVID-19 vaccines and the prolonging of the menstruation cycle, this is one of the first studies to examine the impact the jab may have on the quantity of bleeding.

The European Medicines Agency safety committee defines heavy menstrual bleeding, or heavy periods, as bleeding characterised by larger volumes or longer durations that “interferes with the person’s physical, social, emotional, and material quality of life.”

Co-author Blair Darney said “experiencing an unexpected change in your menstrual cycle can be alarming” but that the abnormalities observed at a population level are small and are likely due to temporary, vaccine-related activation of immune responses.

Nevertheless, more research is needed to fully understand the biological mechanisms at play, and women who do experience changes are encouraged to seek guidance from their clinician.

COVID-19 vaccine trials do not look at the vaccination's impact on menstruation. Fizkes/Shutterstock

The findings build on earlier work from the same research team published in Sep. 2022, when they first identified an average increase in the length of the menstrual cycle of 3.7 days following two doses of a COVID-19 vaccine compared with zero doses.

Women have also reported a range of other pregnancy and menstrual cycle changes after COVID-19 vaccination, including pain, unexpected bleeding, fetal malformation and cardiac arrest, and stillbirth.

However, clinical trials of COVID-19 vaccines do not collect details like menstrual outcomes, limiting the ability of manufacturers, public health agencies, and clinicians to respond to questions about the impact of the vaccine on menstrual health.

It is also challenging to confirm whether medical events that have been observed after vaccination are necessarily related to the vaccine.

“Individuals naturally experience inherent and normal variations in menstrual cycle duration and bleeding patterns, making it challenging to isolate COVID-19 vaccination as a cause,” the researchers wrote in the study which was published on April 10 in the British Journal of Obstetrics and Gynaecology.

Scientist Says Pause the Vaccines

In Sep. 2022, researchers found significantly more pregnancy and menstruation abnormalities following COVID-19 vaccinations than influenza vaccinations, based on reports submitted to the Vaccine Adverse Event Reporting System (VAERS).

A worldwide moratorium on using COVID-19 vaccines in pregnancy was advised until randomised prospective trials of safety in pregnancy and follow-ups on offspring were documented.

“There’s enough of a safety signal in our research in looking at VAERS that we should really take a pause from the vaccines until they are studied more in-depth,” one of the report’s authors, Claire Rogers told The Epoch Times.

In a vaccine safety update published in Nov. 2022, the European Medicines Agency found that “9,000 worldwide cases of heavy menstrual bleeding have been reported after the first, second, and booster doses of Comirnaty and Spikevax,” referring to the Pfizer and Moderna shots.

Following this, the drug regulator recommended adding “heavy menstrual bleeding” as an mRNA COVID-19 vaccine side effect to both vaccines.

Pregnant Women and Vaccines

The current advice for pregnant women about getting vaccinated for COVID-19 is that the benefits of the vaccination outweigh the side effects.

According to Australia’s health department, “COVID-19 can be serious for women who are pregnant. The best way to reduce your risk [is to] get all the COVID-19 vaccinations recommended for your age group or individual health needs.”

However, as COVID-19 is still relatively new and safety evidence still lacking, many pregnant women are hesitant about the jab.

According to a study published in the journal BMJ Open of 6,000 Australian women who were pregnant, or gave birth during the first two years of the pandemic, one in ten of them was hesitant to get a COVID-19 vaccination.

Those who expressed this hesitancy were more likely to live in a state other than New South Wales, were younger than 30, and were also less likely to have pregnancy risk factors.

It is estimated that around a third of pregnant Australian women are fully vaccinated and a third have had no doses, with safety concerns reported as one of the top reasons to decline the vaccination during pregnancy.