Association Between Menstrual Cycle Length and Coronavirus Disease 2019 (COVID-19) Vaccination.
To assess whether vaccination against coronavirus disease 2019 is associated with changes in cycle or menstrual length in vaccinated individuals compared to unvaccinated cohorts. We used the Natural Cycles application to analyze the positively recorded menstrual cycle data. US citizens aged 18-45 years, 3 consecutive cycles before the first vaccination (cycles 4-6), or a normal cycle length of 6 cycles (24-38 days) if not vaccinated there is. Period Included period. Averages within individual variations in cycle and menstrual length were calculated (3 cycles before vaccination vs. the first and second dosing cycles of the vaccinated cohort, and the first 3 cycles vs. the non-vaccinated cohort. Cycles 4 and 5). A mixed-effects model was used to estimate adjusted differences in cycle and menstrual length changes between vaccinated and non-vaccinated cohorts. We included 3,959 subjects (2,403 vaccinated; 1,556 unvaccinated). The majority of the vaccinated cohorts received the PfizerBioN...