Health Canada Recognizes COVID Vaccination Causes Menstrual Issues, But Unable to Determine Prevalence

A sign is displayed in front of Health Canada headquarters in Ottawa in a file photo. Sean Kilpatrick/The Canadian Press

Health Canada says there is a possibility that COVID-19 vaccination causes menstrual issues but it doesn’t know how prevalent it is among women.

“Based on the available evidence, and in the context of the frequency of menstrual irregularities, it is not possible to determine what percentage of COVID-19 mRNA vaccine recipients could experience an increase in menstrual bleeding,“ Health Canada said in a Sept. 18 Inquiry of Ministry tabled in response to questions submitted by Conservative MP Ted Falk.

The department said it conducted a post-marketing safety review on the risk of heavy menstrual bleeding after the Comirnaty and Spikevax COVID-19 vaccines. The review followed reported events of heavy irregular vaginal bleeding and heavy prolonged cycles consistently lasting more than eight days.

According to the department, their findings were “consistent” with those of the United States Food and Drug Administration and the Pharmacovigilance Risk Assessment Committee of the European Medical Association (EMA-PRAC), who performed an in-depth assessment of amenorrhea (absence of menstruation) and heavy bleeding following mRNA COVID-19 vaccines.

The EMA-PRAC found in June 2022 there was “insufficient evidence for causal association between mRNA vaccines and amenorrhea.” Later that year, they released the results of a review of clinical trials, observational studies, and post-marketing surveillance activities, which found there was “at least a reasonable possibility that heavy menstrual bleeding is causally associated with” the Pfizer-BioNTech COVID-19 Comirnaty vaccine.

According to Health Canada, menstrual cycle irregularities are “common during the reproductive years,” independent of vaccination, and stress, infections, and medications could also modify the length, duration, and heaviness of bleeding during the cycle.

A Norwegian study published on Sept. 22 in the peer-reviewed Science Advances journal found that of 21,000 respondents, 252 postmenopausal women, 1,008 perimenopausal women, and 924 premenopausal women reported experiencing unexpected vaginal bleeding following COVID-19 vaccination. They found around half of each group said the bleeding came within four weeks of the first or second dose.

Back in September 2022, an international peer-reviewed study funded by the U.S. National Institutes of Health that examined 20,000 women from Canada, the United States, and Europe also indicated that COVID-19 vaccination was associated with a temporary increase in menstrual cycle duration.

‘Categorically Safe’ for Pregnant Women

Mr. Falk also asked the government about “the scientific basis for government officials’ statements that COVID-19 vaccines are categorically safe for pregnant and breastfeeding women.” Health Canada said this assertion was based on a continuous review of evidence since the vaccines were first authorized in 2020.

The agency said their ongoing national and global vaccine safety monitoring systems had shown “no evidence of any adverse pregnancy or neonatal outcomes” associated with the vaccines. The National Advisory Committee on Immunization (NACI) continues to recommend the use of COVID-19 vaccines in pregnancy and breastfeeding.

“The Public Health Agency of Canada (PHAC) and Health Canada continue to actively evaluate all available data and examine emerging scientific literature to detect any potential short or long-term impacts on fertility and/or pregnancy from COVID-19 vaccination,” the agency said.

The agency also said that the NACI recommends continuous monitoring of data on the safety, immunogenicity, efficacy, and effectiveness of COVID-19 vaccination in pregnancy and breastfeeding as a research priority.

A recent Lancet study found that mRNA from COVID-19 vaccines can end up in breastmilk and can be passed on to infants by their vaccinated mothers. Researchers in the peer-reviewed study detected the mRNA in 70 percent of women who provided breast milk samples up to 45 hours following vaccination.

An August 2021 peer-reviewed study published in Nature also found that lactating mothers who received Pfizer’s COVID-19 vaccine secreted SARS-CoV-2-specific IgA and IgG antibodies into breastmilk, with the largest increase seen three to seven days after their second dose.

During the trials for the mRNA vaccines, both Pfizer and Moderna excluded pregnant and lactating women from their clinical trials. Pfizer also stopped its clinical trial for pregnant women. Human pharmacokinetic studies to assess how the human body interacts with mRNA from COVID-19 vaccines were never conducted.