The Covid-19 vaccine disrupts the normal menstrual cycle in around 25 percent of vaccinated women.
Irregular menstruation was the most common complaint, affecting around 43 percent of the 545 young women who were monitored, and increased menstrual symptoms were reported by 34 percent of them.
Increased pain and cramping affected around one-third, and a similar rate experienced heavy or prolonged bleeding, researchers from the University of Arizona discovered.
Most women reported menstrual problems after they had been given the second dose of Pfizer’s mRNA vaccine. Women who had had a Covid infection were less likely to report menstrual problems after vaccination.
The women were aged between 26 and 33.