Can COVID Vaccine Affect Women's Menstrual Cycles?

Some women have reported changes in their menstrual cycle after getting the COVID-19 vaccine, including earlier, later, heavier or more painful periods. Vaccine trials did not track data on this as a possible side effect, and there is no specific evidence linking the vaccine to menstrual changes. Doctors say periods fluctuate for many reasons, and the lining of the uterus does have immune cells that could respond to the vaccine.