Nearly Half of Healthy Women Experience ‘Menstrual Cycle-Related Symptoms’ After COVID-19 Vaccination: New Peer-Reviewed ‘Women’s Health’ Study

Originally published June 7, 2023 10:01 am PDT

A new peer-reviewed study published on Wednesday in Women’s Health found that mRNA-based SARS-CoV-2 vaccines can negatively affect menstruation, especially in women with certain inflammatory gynecological conditions.

The authors confirmed that COVID-19 vaccination “can have an impact on menstruation, and this impact may be more notable in women with inflammatory gynecological pathologies such as endometriosis.”

Endometriosis is a medical condition characterized by the growth of tissue similar to the uterine lining outside the uterus. This abnormal tissue growth can occur in various locations in the body where it is not supposed to, including the ovaries, fallopian tubes, and supportive tissues that hold the uterus in position.

The researchers’ objective was “to investigate the impact of mRNA-based SARS-CoV-2 vaccines on menstrual cycle-related symptoms in women with endometriosis and assess the effect of hormonal therapy on potential SARS-CoV-2 vaccination-induced menstrual changes,” according to the study.

A total of 848 women who received at least two doses of mRNA-based COVID vaccines were recruited. Four-hundred-and-seven had endometriosis (endometriosis group) and 441 did not (non-endometriosis group).

Through an online survey, the study authors collected data regarding demographics, clinical characteristics, hormonal treatment, and menstrual-associated symptoms in the first and second cycles after vaccination.

In the endometriosis group, 52.6% of patients “self-reported” menstrual-associated changes in the first cycle after vaccination and 29% after the second cycle of vaccination.

Significantly, patients in the non-endometriosis (healthy) group reported similar rates of vaccine-induced side effects compared to patients with endometriosis, demonstrating the mRNA jab negatively affects all women relatively equally, regardless of inflammatory gynecological condition status.

Among the non-endometriosis (healthy) group, 48.8% of patients self-reported menstrual-associated changes in the first cycle after vaccination and 28.1% after the second cycle of vaccination.

The researchers emphasized that “the total symptoms recorded were not different between the two groups.”

However, they did note that “several specific symptoms were statistically more frequent in the endometriosis group. These were pain disorders and fatigue in the first cycle after vaccination and pain disorders, menstrual headache and fatigue in the second cycle after vaccination.”

They also found that healthy women experienced “more frequent” bleeding frequency and regularity disorders. “Bleeding frequency/regularity disorders were found to be more frequent in the non-endometriosis group in the first cycle after vaccination,” the authors confirm.

It’s worth mentioning that patients who were under hormonal treatment in both the endometriosis and non-endometriosis groups “reported fewer changes in menstrual symptoms in the first and second cycle after vaccination compared with those not receiving this treatment.”

“Hormonal treatment may have a protective effect against worsened or new menstrual symptoms induced by COVID-19 vaccination,” the authors write.

However, across both groups, undergoing hormone treatment only lowered the likelihood of patients self-reporting vaccine-induced negative menstrual symptoms by 6.6% after the first vaccination and by 6.8% after a second cycle of vaccination.

“Analysis of the whole population showed that patients receiving hormonal treatment reported fewer changes of menstrual symptoms compared with those not receiving this treatment in the first (46.7% versus 53.3%, respectively; pā€‰=ā€‰0.02) and second cycle after vaccination (24.5 versus 31.3, respectively; pā€‰=ā€‰0.03),” the study reads.

It’s important to note that the patient’s adverse health outcomes caused by the COVID vaccine were self-reported, meaning that more patients could have experienced a vaccine-induced negative health outcome but simply didn’t report it. Such vaccine adverse effects would therefore not have made it into the study.

In fact, fewer than 1% of vaccine adverse events are ever reported, according to a 2010 analysis submitted to the Agency for Healthcare Research and Quality at the U.S. Department of Health and Human Services (DHHS).

“Adverse events from drugs and vaccines are common, but underreported,” write the analysis authors, adding that “[a]lthough 25% of ambulatory patients experience an adverse drug event, less than 0.3% of all adverse drug events and 1-13% of serious events are reported to the Food and Drug Administration (FDA).”

“Likewise, fewer than 1% of vaccine adverse events are reported,” the analysis emphasized.

Read the new Women’s Health study in full here: