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The study suggests that COVID-19 vaccination may be associated with short-term changes in usual menstrual cycle length

In a recent work in the American Journal of Obstetrics and Gynecologythe investigators analyzed the links between vaccination with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and infection with menstrual health.

Study: A prospective study of the association between SARS-CoV-2 infection and COVID-19 vaccination with changes in usual features of the menstrual cycle.  Image Credit: Alina Kruk/Shutterstock
Study: A prospective study of the association between SARS-CoV-2 infection and COVID-19 vaccination with changes in usual features of the menstrual cycle. Credit: Alina Kruk/Shutterstock


In 2021, unsubstantiated reports that the CoV disease 2019 (COVID-19) vaccine or SARS-CoV-2 infection would affect the menstrual cycle triggered extensive media coverage and public interest, such as: B. A quick response from the National Institutes of the United States (US). of Health by funding a SARS-CoV-2 infection and menstrual health network.

Vaccination hesitancy among the general public and vaccination reluctance among adolescents, children and women of reproductive age is now being amplified due to concerns and unfounded information about the impact of COVID-19 vaccination on reproductive health. As a result, the reproductive safety of the COVID-19 vaccine is a new public health concern. Nonetheless, there is still little systematic research on the effects of the SARS-CoV-2 vaccine, or COVID-19, on menstrual health, despite growing public concern and skepticism about the likely adverse reproductive effects of COVID-19 and its vaccination.

About the study

In the present work, researchers examined the correlations between COVID-19 vaccination and SARS-CoV-2 infection with changes in menstrual cycle characteristics in premenopausal health workers participating in an active prospective cohort study. In addition, they examined the duration of such changes, possible variations by vaccine type, and whether stress induced by the pandemic (e.g., mental health changes, stress or regional COVID-19 burden) was responsible for deviations from the usual characteristics of the menstrual cycle.

The team prospectively followed 3,858 premenopausal women from the Nurses’ Health Study 3 (NHS3) who lived in Canada or the United States. They sent follow-up questionnaires to these subjects every two years from January 2011 to December 2021. Nurses also took part in monthly and quarterly supplemental surveys on the SARS-CoV-2 pandemic from April 2020 to November 2021. 2 positive tests and vaccine type.

From pre-COVID baseline data between 2011 and 2016 and post-COVID data in late 2021, the scientists collected information on the regularity and length of the current menstrual cycle. Changes in menstrual cycle regularity and length were also determined using pre- and post-COVID reports. Associations between 1) COVID-19 vaccination and 2) SARS-CoV-2 infection and shifts in menstrual cycle characteristics were assessed using multinomial logistic or logistic regression models.


Study results showed that with a median follow-up of 9.2 years, the median age of the study subjects at the start of the research and the completion of follow-up was 33 years, with a range of 21 to 51 and 42 years to 27 to 56. The Authors recorded 3,527 COVID-19 vaccinations, i.e. 91.4%, and 421, i.e. 10.9%, SARS-CoV-2 infections in the follow-up.

After controlling for behavioral and sociodemographic characteristics, women who had received SARS-CoV-2 vaccinations had a higher risk of prolonged menstrual cycles than unvaccinated women. After accounting for the stresses caused by the pandemic in the analysis, these relationships remained the same. The COVID-19 vaccine was associated with a transition to longer menstrual cycles only in the first six months after vaccination and in women whose pre-vaccination menstrual cycles were short, long, or irregular. Overall, the researchers found that women with long, short, or irregular pre-vaccination menstrual cycles were more likely to experience a transient, i.e., less than six months, increase in typical menstrual cycle length after receiving the COVID-19 vaccine.

Adenovirus vector and messenger ribonucleic acid (mRNA) COVID-19 vaccines have been linked to this menstrual cycle change, suggesting common pathways. Furthermore, behavioral changes and stress related to the COVID-19 pandemic did not explain the associations between SARS-CoV-2 vaccination and changes in menstrual health.

Interestingly, SARS-CoV-2 infection was not associated with changes in the characteristics of the regular menstrual cycle. According to this conclusion, the transient effect of COVID-19 vaccines may differ from the immune response to SARS-CoV-2 infection, which appears to be more widespread and tissue-selective than those associated with vaccines. However, given the small number of affected subjects in the study, this finding should be interpreted with caution.


Study results indicated that SARS-CoV-2 vaccination could be associated with transient changes in the length of the typical menstrual cycle, particularly in women whose pre-vaccination cycles were long, short, or irregular. These results underscore the importance of tracking menstrual health during clinical vaccine trials.

In addition, the current results underscore the need to pay more attention to gender differences in vaccine response, especially given the deployment of COVID-19 vaccine boosters, which represent another opportunity to explore this important topic. The researchers mentioned that future research should evaluate the possible biological processes underlying the links between SARS-CoV-2 vaccination and menstrual cycle changes.

In addition, the team believed that the current study has implications for clinicians, COVID-19 vaccine developers and scientists to better understand the potential fluctuations in the menstrual cycle after vaccination and inform patient expectations.

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