Effects of COVID-19 Vaccines on the Menstrual Cycle: A Cross-Sectional Study

Prior clinical studies that sought to investigate the safety and efficacy of COVID-19 vaccines did not list menstrual cycle changes as a side-effect. However, following reported cases of menstrual cycle disturbances after vaccination, this study sought to examine the link between COVID-19 vaccination and post-vaccine menstrual cycle abnormalities in pre-and post-menopausal women.

A cross-sectional research design approach using online surveys were employed to investigate the link between vaccination and changes in the menstrual cycle. The participants consisted of a cohort of 657 pre-and post-menopausal women, with the majority drawn from the reproductive age group (25-44 years). The inclusion criteria were that participants must have received any type of COVID-19 vaccine, not be pregnant and those that did not have a negative diagnosis in any gynecologic condition. Of the eligible sample size, only 344 participants met the inclusion criteria.

The sociodemographic and menstrual cycle data were collected from an online survey. Data was analyzed using descriptive, inferential chi-square tests, logistic regression, and correlation.

The results partially confirmed the findings from prior studies that COVID-19 vaccination is associated with significant changes in the women’s menstrual cycle flow and menstrual period length even after controlling for age, Body Mass Index, and ethnicity. Other menstrual cycle disturbances such as missed periods, cycle regularity, and spotting/vaginal bleeding were noted to be less significant. However, the extent of menstrual cycle changes was less severe and decreased after the second dose of vaccination. It was found that 11.1% and 37.5% of post-menopausal women reported menstrual symptoms after the first and second dose cycles, respectively.

The study concludes that although COVID-19 vaccines tend to adversely affect women’s menstrual cycle, these changes are short-lived. The findings have important implications in enhancing the success of COVID-19 vaccination programs by reducing cases of vaccine hesitancy among reproductive-age women.