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

By Shanet Susan AlexReviewed by Danielle Ellis, B.Sc.Jul 18 2022

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

Background

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

The vaccine skepticism among the general public and vaccine reluctance among adolescents, children, and women of reproductive age are now heightened because of concerns and baseless information about the COVID-19 vaccination affecting reproductive health. As a result, a new public health concern is the safety of COVID-19 vaccination for reproduction. Nonetheless, there is still little systematic research on the effects of the SARS-CoV-2 vaccine or COVID-19 on menstrual health, despite the growing public concerns and skepticism regarding the probable adverse reproductive effects of COVID-19 and its vaccination.

About the study

In the present work, the researchers examined the correlations between COVID-19 vaccination and SARS-CoV-2 infection with alterations in the typical menstrual cycle features in pre-menopausal healthcare workers participating in an active prospective cohort investigation. Additionally, they looked at the length of such alterations, potential variations by vaccine kind, and whether stress brought on by the pandemic (such as changes in mental health, distress, or the regional COVID-19 burden) was responsible for variances in the usual menstrual cycle traits.

The team prospectively tracked 3,858 pre-menopausal females from the Nurses' Health Study 3 (NHS3) who resided in Canada or the US. They sent follow-up questionnaires biannually from January 2011 to December 2021 to these subjects. The nurses also participated in supplementary surveys monthly and quarterly regarding the SARS-CoV-2 pandemic from April 2020 to November 2021. In surveys performed in 2020 and 2021, respondents self-reported their COVID-19 vaccination status, history of SARS-CoV-2-positive tests, and vaccine kind.

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. Besides, the alterations in menstrual cycle regularity and length were determined from pre- to post-COVID reports. The connections between 1) COVID-19 vaccination and 2) SARS-CoV-2 infection and shifts in menstrual cycle features were evaluated using multinomial logistic or logistic regression models.

Results

The study results indicated that with a median follow-up length of 9.2 years, the median age of the study volunteers at research initiation and the completion of the follow-up was 33 years, ranging from 21 to 51, and 42 years, ranging from 27 to 56, respectively. The authors recorded 3,527 COVID-19 vaccinations, i.e., 91.4%, and 421, i.e., 10.9%, SARS-CoV-2 infections during follow-up.

After controlling for behavioral and sociodemographic characteristics, women who had received SARS-CoV-2 vaccinations had a greater risk of prolonged menstrual cycles than non-vaccinated women. After considering the stress caused by the pandemic in the analysis, these relationships remained the same. Only in the initial six months following immunization and across women whose menstrual cycles were short, long, or irregular antecedent to vaccination the COVID-19 vaccine was linked to a transition to longer menstrual cycles. Overall, the researchers discovered that women with long, short, or irregular pre-vaccination menstrual cycles were more likely to experience a transient, i.e., less than six-month, increase in typical menstrual cycle duration after receiving the COVID-19 vaccine.

Adenovirus-vectored and messenger ribonucleic acid (mRNA) COVID-19 vaccines were linked with this menstrual cycle change, pointing to shared pathways. Further, behavioral changes and stress associated with the COVID-19 pandemic did not explain the associations between SARS-CoV-2 vaccination and alterations in menstrual health.

Interestingly, SARS-CoV-2 infection was not linked with alterations in the regular menstrual cycle features. According to this inference, the transient impact of COVID-19 vaccines may vary from the immune reaction to SARS-CoV-2 infection, which seems more widespread and tissue-selective than those associated with vaccines. Nevertheless, given the study's small number of affected subjects, this finding should be interpreted carefully.

Conclusions 

The study findings depicted that the SARS-CoV-2 vaccination might be linked to temporary alterations in the length of the typical menstrual cycle, especially in women whose cycles were long, short, or irregular earlier to vaccination. These findings highlight how crucial it is to track menstrual health throughout vaccine clinical studies.

Moreover, the current findings emphasize the need for paying more attention to gender-based disparities in vaccine reaction, particularly in light of the deployment of COVID-19 vaccine booster shots, which will present yet another chance to research this crucial topic. The researchers mentioned that future investigations should evaluate the possible biological processes underlying the associations between SARS-CoV-2 vaccination and alteration in the menstrual cycle.

Furthermore, the team believed that the current study has implications for clinicians, COVID-19 vaccine developers, and scientists in better comprehending the potential variation in the menstrual cycle following vaccination and informing patient expectations.