COVID-19 vaccine side effects on menstrual disturbances among Iranian women.

Background: Many studies reported of menstrual disturbances as possible side effects of COVID-19 vaccination. Our objective was to evaluate the association between vaccination and the occurrence of menstrual disturbances among Iranian women. Methods: We used to google form questionnaires to collect reports of menstrual disturbances from 455 women aged 15-55 years in Iran. We estimated the relative risk of menstrual disturbances according to vaccination in a self-controlled case-series design after vaccination. We examined the occurrence of such disorders after the first, second and third doses of vaccine. Results: Findings The prevalence of menstrual disturbance was more in latency and heavy bleeding than others disorder after vaccination, although ֮ %50 of women doesn't have any disturbance. We observed increased risks after vaccination also for other menstrual disturbances, in menopausal women too (>10%). Discussion: Menstrual disturbances were generally common regardless of vaccination. We found a significant increase in menstrual disturbances after vaccination, particularly for latency and 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 of immune system stimulation and relation to hormonal secretion.