Johns Hopkins Medicine’s Department of Gynecology and Obstetrics is one of five institutions selected by the National Institutes of Health (NIH) to conduct research to explore the potential impacts of COVID-19 vaccination on menstruation. The five one-year grants, totaling $1.67 million, are funded by NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development and the NIH Office of Research on Women’s Health.

The NIH research grants were established after many women reported irregular menstrual periods and other menstrual changes after getting the COVID-19 vaccines.

“There may be several reasons why a woman might experience unscheduled menstrual bleeding, abnormal periods or bleeding that is heavier than usual,” says lead investigator Mostafa Borahay, M.D., Ph.D., associate professor of gynecology and obstetrics at the Johns Hopkins University School of Medicine. “This research will help us better understand if there’s a real link between the COVID-19 vaccines and these menstrual changes, or if it’s something else, such as lifestyle changes or pandemic-related stress.”

Borahay and his team hypothesize that the immune response following vaccination may bring immune cells into the endometrium (uterus). This, say the researchers, may result in the menstrual irregularities that women are reporting.

“If there’s a relationship between the COVID-19 vaccines and the menstrual changes, we need to know how it happens,” says Borahay. “Therefore, we plan to examine the response of the endometrium to the COVID-19 vaccination at the biological level.”

Menstruation, or a period, is part of a woman’s monthly reproductive cycle. Each month, a woman’s uterus prepares for pregnancy and thickens its walls by increasing the levels of two hormones, estrogen and progesterone. But when pregnancy does not occur, the uterus sheds its lining as the blood and mucus making up the menstrual flow that leaves the body through the vagina during the period.

For the study, the researchers will collect data from different sources. “Through a collaboration with Clue, a period and ovulation tracking app, we will gather unidentifiable data from users about their menstrual cycle before and following COVID vaccination,” says Malak El Sabeh, M.D., a postdoctoral fellow working on the project in Borahay’s laboratory.

Borahay is available for interviews.