This is not a norm for me — my periods are usually light with spotting at the beginning of my cycle, ” one COVID-19 vaccine recipient reported to the CDC system.... Within 72 hours of the vaccine I had light menstruation that lasted for 24 hours, ” another person reported. The NIH-funded studies will be prospective, Bianchi said.... They will include a control group and monitor potential menstruation changes in people who have not been vaccinated yet after they receive a COVID-19 vaccine....