Operational definitions
Normal menstrual cycle: A normal menstrual cycle is regular, and has a frequency of 24-38 days, occurring for 7 days, with 5-80 ml blood loss.15
Premenstrual syndrome: It includes clinically significant somatic and psychological manifestations occurring during the luteal phase of the cycle, causing considerable distress and impairment in functional capacity.16
Fully vaccinated against COVID-19 infection: According to the Centers for Disease Control and Prevention (CDC) individuals who have received their primary series (two doses of COVID-19 vaccine) are considered fully vaccinated after two weeks of their second dose, irrespective of booster doses.17
Not Fully vaccinated against COVID-19 infection: Those who received a second dose less than 2 weeks ago or those who didn’t receive their second dose of a two-dose vaccine.17
Sample size : Sample size was calculated assuming that 50% of the subjects in the population had the factor of interest, with a design effect of two and an expected response rate of 80%, as 961 (with 5% absolute precision, 95% confidence and failure to a response rate of 10%). Since six centers were included as a part of the study, so a total of 5766 sample size was considered. The sample size was calculated using a free online statistical calculator (statulator).18
Sampling method: Consecutive sampling was done till the desired sample size of 961 was achieved at each center.
Flow chart