WOMEN HEALTH

Your period may be late after Covid-19 vaccination – study

Research shows an average change of less than one day in overall cycle duration following vaccination, no changes to period length

In Summary

•“Vaccine- related menstruation disturbance may be linked to the body’s immune response to the vaccine,” Edelman said.

•For some people their periods were late while others reported painful or heavier bleeding than usual .

Image: PEXELS

Shortly after coronavirus vaccines were rolled out about a year ago, women started reporting abnormal menstrual cycles after receiving the shots.

For some people, their periods were late while others reported painful or heavier bleeding than usual.

Some postmenopausal women who had not had a period in years even said they menstruated again.

Image: Courtesy: Oneclub.org

Researchers at Oregon Health and Science University in collaboration with investigators from Natural Cycles, an app that is used by millions of women around the world looked at records from nearly 4,000 women.

The participants included 1,556 who were unvaccinated and 2,403 who were vaccinated; all aged between 18 to 45 years and recorded their periods in six months.

In the study, they found out that participants experienced a 0.71-day increase in menstrual cycle length following a single dose of Covid-19 when compared with menstrual cycles, prior to vaccination.

Participants who received two doses of the Covid-19 vaccine during the same cycle experienced a change of about two days.

A woman tracking her flow
A woman tracking her flow
Image: Courtesy: Dr. Jolene Brighten

What really lead to the delay?

Alison Edelman, MD and professor of Obstetrics and gynaecology at the Oregon Health and Science University School of Medicine said that although more research is needed to understand the causal relationship between Covid-19 and menstruation cycle length, the vaccination might have something to deal with the biological connection between the immune system and the reproductive system.

“Vaccine-related menstruation disturbance may be linked to the body’s immune response to the vaccine,” Edelman said.

“Currently, we know the available Covid vaccine are effective at activating the immune system. The immune system creates a temporary increase in small proteins called cytokines, which can briefly impact a person’s ability to regulate the menstrual cycle; resulting in the temporary changes.”

More research is needed to understand the relationship between the shots and the menstrual cycle as well as the effect booster shots may have as well.

Image: Courtesy: Johns Hopkins Medicine,

What does this mean for you?

Women are advised to track their flows either on a diary or an app to note any period delays and symptoms.

An average of fewer than two days is no cause for concern and doesn’t warrant medical attention, however, if a course of bleeding goes for more than eight days or there are noticeable changes over the course of three or more months, consultation with a doctor is necessary.

Edelman hopes that the study can provide answers and validation to individuals who experienced menstrual disruption following vaccination.

“As a clinician, I can help provide them with information about what to expect with vaccination, which might include a slight variation in their cycle length, and have them prepared for this possibility so that they do not need to worry,” she said.

Overall, the vaccines are safe and effective in curbing hospitalization and research has shown it does not impact fertility in men and women.