Share to Pinterest Researchers have recently been looking into the possible impact of COVID-19 vaccines on the cycle. Stringer/Anadolu Agency via Getty Images
- The impact of the COVID-19 vaccine on menstruation was not measured during any of the clinical trials, but studies are now looking at people’s reports to see if there is a link.
- A recent study linked the COVID-19 vaccine to heavier menstrual flow and unexpected vaginal bleeding in some individuals.
- Reports of changes in menstrual cycles indicate that they are temporary and short-lived, but women and people who have or have had periods need reliable information to make informed choices and hopefully combat hesitation about the vaccine.
There are tens of thousands of reports of menstrual cycle changes around the world following a COVID-19 vaccination, but the link has yet to be proven or disproved.
This is partly due to the failure of drug companies to include questions about menstruation in their trials to date.
Dr Vicky Male, a lecturer in reproductive immunology at Imperial College London in the UK, developed vaccine protocols for clinical trials of the Ebola vaccine. She explained why not capturing menstrual data during the COVID-19 vaccine trials is a missed opportunity in an email to Medical News Today:
“Because clinical trials are double-blind, even the very simple question of ‘Have you noticed any change in your menstrual bleeding or had unexpected vaginal bleeding?’ would be extremely powerful: a control group means we’ll have a good idea of the background rate of these changes in the relevant population and the fact that it was blinded meant that people’s expectations of seeing a change would not affect the reports. I hope that in the future a simple question like this will be included routinely.”
“Investigate if and how [COVID-19] vaccination affects menstrual periods and breakthrough bleeding is catch-up because this information was not collected during the trials. — Dr. Vicky Male
The first study, funded by the National Institutes of Health to investigate the link, was published in January 2022 and showed that the vaccination could affect the cycle but not the length of the menses.
Now, a new study looks not only at changes in menstrual flow in those with regular menstrual cycles, but also at unexpected vaginal bleeding in people who previously had periods but no longer due to use of hormonal contraception, menopause or hormone-based treatment skirt.
To investigate whether or not there is a link between menstrual changes or unexpected vaginal bleeding after vaccination, a team led by Dr. Kathryn Clancy of the University of Illinois at Urbana-Champaign, Champaign, Illinois, set up a study of vaccinated people who were not had had COVID-19 and collected data on people’s ethnic identity, gender identity, age and vaccination received.
First lead author Dr. Kathryn Lee, a postdoctoral researcher at Washington University in St. Louis, Missouri, said in an interview with MNT that they did not want to delay participants’ vaccinations.
“We chose to do this study design because we are very pro-vaccination. So we didn’t want to try to enroll people who had been vaccinated or hadn’t been vaccinated, or tell people to wait to get vaccinated. We were like, as soon as you can get it, you should still definitely get vaccinated.”
“But what we wanted to hear about were people’s experiences because of the variety of stories that came in when [Dr. Kathryn Clancy] tweeted about her period last February.” – Dr. Kathryn Lee
The researchers shared the survey on Twitter and other social media platforms and then analyzed the analyzed data collected between April 7, 2021 and June 29, 2021. Nine out of 10 of the 39,129 participants identified as female, while one in 10 participants identified as as gender diverse.
Participants were asked about their menstrual flow and cycle length and medical history. They were then asked about their menstrual cycle experience after the first and second doses of their COVID-19 vaccines.
Of the participants with regular menstrual cycles, 42% reported bleeding more heavily than usual, while 44% reported no change after vaccination.
Of the postmenopausal individuals who responded to the study, 66 percent reported breakthrough bleeding, along with 71 percent of those on long-acting reversible contraceptives and 39 percent of those on sex-affirming hormones.
Additional analysis found that respondents with gynecological conditions were at greater risk of more severe bleeding after vaccination. Those who experienced fever and fatigue after vaccination, were previously pregnant or gave birth, or who usually had light menstrual cycles were also more likely to report heavier bleeding after a COVID-19 vaccination.
Latino and Hispanic respondents were more likely than any other ethnic group to report heavier bleeding after vaccination if they had regular menstrual cycles and to report breakthrough bleeding if they were postmenopausal.
The inclusion of participants recruited after vaccination may introduce some bias because people are more likely to participate in a study if they believe they have been affected, Dr. Male said in an email.
“We can’t use this survey to determine how common it is to experience a change after a vaccination because people who experience a change are more likely to complete the survey, but we can look for patterns that can give us an idea of who more at risk of undergoing change,” she said.
Dr Clancy told MNT that the aim of the project was never to estimate prevalence as only a prospective study could do that. She said they tried to draw attention to the problems people were experiencing after being met with distrust and unfair treatment.
Dr Clancy said they aimed to “[t]collect those experiences and understand them better and give patients a real voice in this phenomenon that they have somewhere to share what’s going on.
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