US Research Team: "Vaccinated Women Experience Temporary Menstrual Cycle Changes... Recovery After 1-2 Months"

[Image source=AP Yonhap News]

[Asia Economy Reporter Junhyung Lee] A study has found that women who received the COVID-19 vaccine experienced a temporary change in their menstrual cycle, with the cycle lengthening by about one day, before returning to normal after one to two months.

On the 6th (local time), The New York Times (NYT) reported that a joint research team from Yale School of Medicine, Oregon Health & Science University, and Brown University's Warren Alpert Medical School investigated menstrual cycle changes before and after vaccination in about 4,000 women using a menstrual cycle tracking application (app). According to the NYT, this study is the first to confirm women's claims that their menstrual cycles lengthened or that they experienced changes in menstrual pain and bleeding volume after the COVID vaccine rollout began.

The research results were published in the latest issue of the international journal Obstetrics & Gynecology. The research team collaborated with Natural Cycles, the developer of a menstrual cycle tracking app used by millions of women worldwide, to examine the real-time menstrual cycle data of 2,400 vaccinated and 1,550 unvaccinated participants over six months. The study participants were U.S. residents aged 18 to 45.

The investigation revealed that the menstrual cycle of vaccinated individuals lengthened by an average of about one day during the cycle that included the vaccination day compared to before vaccination. The vaccinated group’s cycle extended to 29 days but returned to 28 days after one or two months. In cases where two vaccine doses were administered during a single menstrual cycle, the cycle lengthened by up to two days. However, no menstrual cycle changes were observed in the unvaccinated group during the study period.

Professor Hugh Taylor of Yale University stated, "This study is among the first to confirm women's reported experiences of menstrual cycle changes following COVID vaccination," adding, "The changes in the menstrual cycle were minor and appear to be temporary." He further noted, "While having one or two altered cycles can be annoying, it is not medically harmful. However, postmenopausal women experiencing bleeding, whether vaccinated or not, should consult a doctor as it could indicate a serious condition."

However, the research team noted that since the study was conducted on menstrual cycle app users residing in the United States, there are limitations in generalizing the findings to populations in other countries. It remains unclear how COVID-19 vaccines affect menstrual cycles or whether other vaccines have similar effects.

Even women with regular menstrual cycles experienced irregularities. Since the menstrual cycle, regulated by hormones secreted by the ovaries and other organs, can be influenced by environment, stress, and lifestyle changes, variations can occur. Dr. Diana Bianchi, director of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, said, "A menstrual cycle lengthening by about one day is not something to worry about," and added, "I hope this study encourages vaccine developers and clinical trial researchers to pay more attention to menstrual cycles."

This content was produced with the assistance of AI translation services.