Authored by Mary Gillis via The Epoch Times (emphasis ours),
Norwegian scientists have discovered an unusual side effect in COVID-19-vaccinated women who don’t menstruate: atypical vaginal bleeding after injection with the Moderna and Pfizer vaccines.
Researchers studied close to 22,000 women across different reproductive aging stages over about nine months and found that 3.3 percent of postmenopausal, 14.1 percent of perimenopausal, and 13.1 percent of premenopausal women experienced at least one unexpected bleed after receiving the COVID-19 shot, according to the authors of the study published in Science Advances.
About half of the bleeds were said to have occurred within the first four weeks of getting the vaccine. Postmenopausal women’s risk of bleeding was two to three times higher during the 28 days after injection than before receiving the shot. The link was stronger in perimenopausal and premenopausal women, with both groups showing a three- to fivefold elevated risk. Perimenopausal women are typically in their 40s and have begun experiencing some menopause symptoms but can still get pregnant, while premenstrual women have no menopause symptoms.
Researchers also found a difference in women's susceptibility when given one shot over the other. Premenopausal women were at a 32 percent higher risk of vaginal bleeding after a dose of the Moderna vaccine than the Pfizer.
How Is Vaccination Linked to Bleeding?
Study author Kristine Blix and her colleagues at the Norwegian Institute of Public Health in Oslo drew from questionnaire data from an ongoing population health survey to investigate COVID-19 vaccines and unexpected bleeding in the three groups.
“We had already, from the early pandemic, biweekly questionnaires going out to cohort participants to monitor effects of the pandemic,” Ms. Blix told Nature.
Responses to the 2021 questionnaire indicated that some women experienced unusually heavy menstrual bleeding after receiving the vaccine. "This urged us to ask for bleeding patterns in a structured manner,” she said.
Ms. Blix's team didn't investigate the reasons for the unexplained bleeding, and no conclusive evidence supports that the shot caused it. However, one theory is that the SARS-CoV-2 spike protein used in the vaccines may be a culprit.
"Increased risk after both Comirnaty (Pfizer) and Spikevax (Moderna) suggest a mechanism related to the severe acute respiratory syndrome coronavirus (SARS-CoV-2) spike protein and not to other vaccine components," the authors wrote in the paper. "This is also supported by a higher risk observed after Spikevax in premenopausal women." Possible pathways to induce the bleeding may stem from a spike protein-related immune response or an endometrial expression of the angiotensin-converting enzyme 2 (ACE2) receptors that serve as the virus' entry point, they continued.
A study published in February that examined close to 8,000 women found abnormal bleeding to be a common side effect of the Pfizer vaccine. Most women experienced excessive bleeding between their vaccination date and their next menstrual period, authors wrote in the paper, recommending further investigation into the events and the possible long-term consequences of vaccine-induced vaginal bleeding.
In 2022, The Lancet published a study where researchers showed that a cohort of nearly 64,000 respondents ages 18 and older experienced menstrual irregularities or vaginal bleeding in the form of altered menstruation timing and severity of menstrual symptoms to menopausal bleeding and resumption of menses.
In contrast, a 2023 study published in Vaccine showed premenopausal women vaccinated for COVID-19 were no more likely to report irregular menstrual cycles or heavier bleeds after the shot than unvaccinated women. However, the authors acknowledged about a one-day delay or one-day longer cycle in vaccinated versus unvaccinated women.
Possible Causes of Irregular Vaginal Bleeding
Irregular bleeding may be caused by several factors ranging from stress to more serious underlying medical conditions, including:
- Pelvic inflammatory disease.
- Polycystic ovary syndrome.
- Primary ovarian insufficiency.
- Thyroid or pituitary gland disorders.
- Uterine or ovarian cancer.
Medications and pregnancy complications may also cause irregular bleeding. These include:
- Birth control pills.
- Medications including steroids or blood thinners.
- Miscarriages or an ectopic pregnancy.
- Surgeries, scarring, or blockages in a woman's uterus, ovaries, or fallopian tubes.
FDA Still Recommends the Vaccine
On Sept. 11, the U.S. Food and Drug Administration (FDA) authorized an updated COVID-19 vaccine for emergency use—one "formulated to more closely target currently circulating variants and to provide better protection against serious consequences of COVID-19, including hospitalization and death."
“Vaccination remains critical to public health and continued protection against serious consequences of COVID-19, including hospitalization and death,” said Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, in a press release. “The public can be assured that these updated vaccines have met the agency’s rigorous scientific standards for safety, effectiveness, and manufacturing quality. We very much encourage those who are eligible to consider getting vaccinated.”