Reports from women who say that their menstrual cycles have changed in duration and intensity after a Covid vaccination are widespread, and yet the influence on menstruation is limited and temporary, according to new research. Based on studies in the US and Norway in which the periods of thousands of women were monitored for six cycles using a period app, reproductive physician Victoria Male from the Imperial College London concludes that the menstrual fluctuations are “small.” “The findings from both these studies are reassuring,” Male says in a report published in January in the scientific j…