hen Covid-19 vaccinations were first rolled out, vulnerable elderly people tended to be first in line. Then, as a younger demographic took their turn, there were reports from many women of what seemed like a strange side effect — changes to their menstrual periods. Some noticed cycle length was different after vaccination, others that their period was heavier than usual. By May 2022 in the UK alone, 39,839 women had reported these sorts of changes.
