A study by Oregon Health & Science University shows that COVID-19 vaccination timing can slightly and temporarily alter menstrual cycle length, especially when given in the cycle’s first half. These findings aim to reassure and inform about minor changes, highlighting the need for more research on menstruation’s significance for health and fertility.
“Understanding these changes on a population level allows us to more effectively counsel patients about what to expect with a COVID-19 vaccine,” said Alison Edelman, M.D., M.P.H., the study’s lead author and professor of obstetrics and gynecology and division director of Complex Family Planning in the OHSU School of Medicine. “We hope this work helps validate the public’s experiences and ease fears and anxiety around vaccination.
Analysis shows that individuals who were vaccinated in the follicular phase experienced, on average, a one-day increase in cycle length when compared with their pre-vaccination cycle average. Changes typically resolved in the cycle after vaccination.While there is now a large body of evidence demonstrating that the COVID-19 vaccine is associated with temporary menstrual cycle disturbances, the exact biological mechanism for these changes is still unknown.