The article says that an extremely rare side effect of swelling of the heart has occurred in roughly 100 people. So as a result they've added this to the side effects list.
So if over 4000 women have logged irregular and painful periods as a side effect why on earth has it not been logged as an official side effect!?!?
www.thesun.co.uk/news/15532780/new-side-effect-added-covid-vaccine-list/