The first reports that several women experienced menstrual disturbances after coronavirus vaccination came early in summer 2021. The Norwegian Institute of Public Health (NIPH) promptly introduced questions about menstrual disturbances into ongoing population studies. The first results indicated that coronavirus vaccination can affect menstruation in women between the ages of 18 and 30. A new study from the NIPH published in Vaccine also shows an increased incidence in girls between 12-15 years of age. "4.7 percent of the participants reported that their last period before vaccination was heavier than they usually experience. After vaccination, 7.3 percent reported that the first...