---
title: Does COVID-19 vaccination cause changes to menstrual cycles? | Niyora
description: Nearly 60 percent of women reported menstrual changes after COVID-19 vaccination, mainly in bleeding intensity and cycle length. The changes appeared temporar
url: https://niyora.com/research/papers/association-between-covid-19-vaccination-and-alterations-in-the-menstrual-cycle-2025/
---

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- Does COVID-19 vaccination cause changes to menstrual cycles?

Cohort study, 2025

# Does COVID-19 vaccination cause changes to menstrual cycles?

Nearly 60 percent of women reported menstrual changes after COVID-19 vaccination, mainly in bleeding intensity and cycle length. The changes appeared temporary and did not cause serious health problems.

 Early or limited evidence

Mexican university women over 18 with regular cycles and at least one COVID-19 vaccine dose

## What they did

Online survey of Mexican university women who had received at least one COVID-19 vaccine. Women reported changes in their menstrual cycles before and after vaccination from August to December 2024. The study excluded women with other factors affecting menstruation.

## What they found

59.8 percent of participants reported menstrual alterations. The main changes were in bleeding intensity (82.6 percent), period length (55.4 percent), and cycle frequency (31.5 percent). Some women also reported emotional symptoms.

## What it means for you

There may be a temporary link between COVID-19 vaccination and menstrual changes in some women, without serious clinical consequences. The study was small, based on women's recollection of their cycles, and included only university women in one country.

59.8%

reported any menstrual alterations

82.6%

reported changes in bleeding intensity

55.4%

reported changes in period length

## About the study

Original title Association Between Covid-19 Vaccination and Alterations in the Menstrual Cycle Authors Avila Hernández Nelly Julieta Journal Clinical Research and Clinical Trials Year 2025 Study design Cohort study Participants 19 What was tested COVID-19 vaccination Open access Yes Read the paper [doi.org/10.31579/2693-4779/278](https://doi.org/10.31579/2693-4779/278) Original abstract

The COVID-19 pandemic, declared in March 2020 by the WHO, prompted global health strategies, including mass vaccination campaigns. In record time, vaccines were developed with various biotechnological platforms (mRNA, viral vectors and inactivated viruses), which demonstrated high efficacy in reducing hospitalizations and deaths from SARS-CoV-2. Its adverse effects were mostly mild and transient. However, as immunization progressed, anecdotal reports emerged about possible alterations in the menstrual cycle, such as changes in the duration, intensity of bleeding, frequency between cycles and atypical premenstrual symptoms. Although in cases such as the HPV vaccine this possibility had already been raised, a direct causal relationship has not been established. Objective: To analyze the possible association between vaccination against COVID-19 and menstrual alterations in Mexican university women. Materials and methods: Observational, longitudinal and analytical study by means of a digital survey applied between August and December 2024 to women over 18 years of age, active or graduated from the FES Iztacala, with regular cycles and at least one dose of COVID-19 vaccine. Those who had factors that altered their menstruation were excluded. The survey collected general data, pre- and post-vaccination menstrual characteristics, lifestyle, and vaccine type. Results: 59.8% of the participants reported menstrual alterations. The main changes were in bleeding intensity (82.6%), period length (55.4%), and frequency (31.5%). Physical and emotional symptoms were also reported. Conclusions: The results suggest a possible temporal association without serious clinical consequences.

Reproduced under CC-BY.

## Topics

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