The Effect of the Covid-19 Vaccine and Covid-19 Infection on Menstrual Cycle Length: An Analysis of 10,922 Patients

ABSTRACT

Objective: To evaluate whether receiving a COVID-19 vaccine or infection with COVID-19 had an impact on the length of menstrual cycles in women of reproductive age. Material(s) and Method(s) Cross-sectional, nationwide study of reproductive age females users of the menstrual tracker app Glow. All participants were aged 18-55 and lived in the United States. From 3/3/22 to 4/7/22, participants who had at least 6 months of continuous app use prior to and after April 2021 (defined as logging of menstrual cycle data) were invited to participate in a short questionnaire asking about vaccine status, COVID infection status, and symptoms around the time of vaccination and/or infection. This study was approved by the University of California IRB. Result(s) Out of 218,977 eligible individuals, 11,591 completed the study. 10,922 (representing 269,278 cycles) were included. Some patients were excluded due to not having 6 cycles of data before or after the vaccine or infection and for reporting hormonal birth control use. 75% received two doses of the vaccine (60% Pfizer-BioNTech, 34% Moderna, and 7% J&J), 5% received one dose (63% Pfizer-BioNTech, 37% Moderna, and 1% J&J), and 20% were unvaccinated. There was no change in menstrual cycle length after one or two doses of the vaccine (-0.01 day, 95% CI -0.05 to 0.03 and -0.01 days, 95% CI -0.06 to 0.03, respectively), as was the case in unvaccinated patients (0.05 days, 95% CI -0.02 to 0.12). While participants who reported a COVID infection were noted to have a shorter first cycle after infection (-0.07 days, 95% CI -0.11 to -0.02), this difference was not clinically significant. There were no differences in months 2-6 after infection, or in average cycle length in the 6 months after infection. Of note, whether a patient was symptomatic or asymptomatic with vaccination or infection did not meaningfully impact the menstrual cycle length. Conclusion(s) The COVID-19 vaccine and COVID-19 infection do not result in meaningful menstrual cycle changes compared to unvaccinated or uninfected individuals, respectively. Impact Statement This is the largest study to date to describe that the COVID-19 vaccine and COVID-19 infection do not appear to result in menstrual cycle changes and adds to the body of literature supporting the safety of the COVID-19 vaccine. Support No financial support. Copyright © 2022