A study put out showed that women experienced menstrual cycle changes after receiving covid vaccines. The study was supported in part by the University of Illinois Beckman Institute for Advanced Science and Technology, the University of Illinois Interdisciplinary Health Sciences Institute, NIH T32CA190194 (MPI: Colditz/James), and by the Foundation for Barnes-Jewish Hospital and by Siteman Cancer Center (KMNL).
A new study out shows that women who received a Covid vaccine are far more prevalent than previously acknowledged to see a change in their monthly cycles than those who are unvaccinated. The study found that 56% of women experienced changes in their cycle after being double-vaccinated against Covid.
The researchers investigated the issue of a change in menstrual bleeding patterns among a convenience sample of currently and formerly menstruating people using a web-based survey.
From the sample, the researchers found that 42% of women with a regular menstrual cycle bled more heavily than usual while 44% reported no change after being vaccinated. While respondents who typically do not menstruate, 71% of people on long-acting reversible contraceptives, 39% of people on gender-affirming hormones, and 66% of post-menopausal people reported breakthrough bleeding.
Researchers also found that increased/breakthrough bleeding was significantly associated with age, systemic vaccine side effects, history of pregnancy or birth, and ethnicity.
“In terms of who was more likely to see this effect in our sample … people who were Hispanic were more likely to see heavier bleeding,” said researcher and study author Katharine Lee, Ph.D. “People who were older in the pre-menopausal group were more likely to see heavier bleeding. (People) diagnosed with … something like endometriosis or fibroids were more likely to see heavy bleeding.”
Another peer-reveiwed study published in Obstetrics & Gynecology last month saw researchers tracking 4,000 women aged 18-45 years-old menstrual cycle who were unvaccinated or received the Pfizer-BioNTech, Moderna or Johnson & Johnson vaccines.
Results showed that cycles were delayed on average by less than a day after the first dose and up to two days for people who received two shots within a single cycle, regardless of vaccine brand.
A European study of 4,000 women in Norway found that 15% reported an increase in their menstrual pains after the first vaccine and 14% reported heavier bleeding.
Findings The prevalence of any menstrual disturbance was 37.8% prior to vaccination. The relative risk of more heavy bleeding than usual during the exposed compared to unexposed period for first dose vaccination was 1.90 (95% CI: 1.69-2.13), while it was 1.84 (1.66-2.03) for the second dose. The proportion with menstrual disturbances in the most recent menstruation prior to the second vaccine dose was roughly the same as before the first vaccine dose. The risk of heavy bleeding after the second dose, given that it had occurred after the first, was 65.7%. We observed increased risks after vaccination also for other menstrual disturbances.
Interpretation Menstrual disturbances were generally common regardless of vaccination. We found a significant increase in menstrual disturbances after vaccination, particularly for heavier bleeding than usual, longer duration and for short interval between menstruations. Mechanisms underlying these findings may involve bleeding disturbances in general, as well as endocrine alterations.
