- The impact of the COVID-19 vaccine on menstruation has not been measured in 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 people.
- Reports of changes in the menstrual cycle indicate that they are temporary and short-lived, but women and people who have or are menstruating need reliable information to make informed choices and, hopefully, combat vaccine hesitancy.
This is partly because pharmaceutical companies have not included questions about menstruation in their trials to date.
Dr Viki Malelecturer in reproductive immunology at Imperial College London in the UK, designed vaccination protocols for clinical trials of the Ebola vaccine. She explained why not capturing menstruation data during COVID-19 vaccine trials was a missed opportunity in an email to Medical News Today:
“Because clinical trials are double-blind, even the very simple question ‘Did you notice a change in your menstrual bleeding or did you experience unexpected vaginal bleeding?’ would have been extremely powerful: the control group means that we would have a good idea of the background rate of these changes in the population of interest and the fact that it is blinded means that people’s expectations of seeing a change would not have affected reports. In the future, I hope that a simple question like this will be systematically included.
“Research to know if and how [COVID-19] vaccination affects menstruation and breakthrough bleeding has caught up since this information was not collected during the trials.
— Dr. Viki Male
The first one study to be published with funding from the National Institutes of Health to investigate a link was published in January 2022 and showed that vaccination could affect the cycle but not the duration of periods.
Now a new study examined not only changes in menstrual flow in people with a regular menstrual cycle, but also unexpected vaginal bleeding in people who once had their periods but no longer do so due to use of hormonal contraception , menopause or gender-affirming hormone therapy.
To determine whether or not there was a link between changes in menstruation or unexpected vaginal bleeding after vaccination, a team led by Dr. Kathryn Clancy from the University of Illinois at Urbana-Champaign, Champaign, IL designed a survey for vaccinated people who had not had COVID-19 and collected data on ethnic identity, gender identity , age and vaccination received from people.
First lead author Dr Katharine Leea postdoctoral researcher at Washington University in St. Louis, MO says DTM in an interview that they did not want to delay participants’ vaccinations.
“We chose to do this study design because we are very pro-vaccine. So we didn’t want to try to enroll vaccinated or unvaccinated people or tell people to wait to get vaccinated. We were like, as soon as you can get it, you should always get vaccinated.
“But what we wanted to hear were people’s experiences because of the variety of stories that came up when [Dr. Kathryn Clancy] tweeted about her period in February last year.
— Dr. Katharine Lee
The researchers shared the survey on Twitter and other social media platforms, 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 women, while one in 10 participants identified as gender diverse.
Participants were asked about their period flow, cycle length and medical history. They were then asked about their experiences of their menstrual cycle after the first and second doses of their COVID-19 vaccines.
Among participants with a regular menstrual cycle, 42% reported bleeding more heavily than usual, while 44% reported no change after being vaccinated.
Among postmenopausal people who responded to the survey, 66% reported breakthrough bleeding, along with 71% of people on long-acting reversible contraceptives and 39% of people on gender-affirming hormones.
Further analysis revealed that respondents with gynecological problems were at higher risk for heavier bleeding after vaccination. Those who had fever and fatigue after vaccination had previously been pregnant or had given birth or who normally had a light menstrual flow were also more likely to report heavier bleeding after the COVID-19 vaccination.
Hispanic and Latino respondents were more likely than any other ethnic group to report heavier bleeding after vaccination if they had a regular menstrual cycle and to report breakthrough bleeding if they were in menopause.
Including participants recruited after vaccination could have some bias, as people were more likely to participate in a study if they thought they were affected, Dr Male said in an email.
“We cannot use this study to determine how common it is to experience a change in flow after vaccination because people who have undergone a change are more likely to respond to the survey, but we can look for patterns that might give us an idea of who is more at risk of undergoing change,” she said.
Dr Clancy said DTM that the purpose of the project was never to assess prevalence because only a prospective study can do that. She said they tried to draw attention to the issues people were having after facing disbelief and unfair treatment.
Dr Clancy said they aimed to “[t]ry and collect these experiences and understand them better, and give patients a real voice in this phenomenon that they have a place where they can share what is happening.