The Covid Vaccine and Periods. What the data shows.

About three decades into the past, if we were asked to envision the year 2022, we’d probably see it clad in the grandeur of technology and science. Flying cars, teleportation, and peak space exploration may be some of the expectations of the year ‘22. However, our beautiful conceptualized vista has all but dissolved in acrimony. After two tiring years of alternating between lockdowns and new outbreaks, COVID-19 has shown no signs of piping down.

As we saunter into our third year of the global pandemic, there is little hope for our society to return to its old routine of normal. Instead, we are looking forwards to a world that embraces a strengthened healthcare system, reshaped economy, and a well-renewed and brighter “new normal”. However, despite the enactment of movement restrictions, social distancing norms, and stay-at-home orders, the COVID-19 pandemic has resulted in a devastating cycle of morbidity and mortality.

The vast majority of the global population remained vulnerable to COVID-19 and this brought on the innovation of the century - THE vaccine. Today, we are bombarded with a wide variety of vaccines that apparently do much of the same thing - protecting us from debilitating hospitalization from the virus. We must, however, address the red elephant in the room - the vaccine’s ability to affect menstruation.

COVID-19 vaccine and menstruation

The global vaccine development efforts have sky-rocketed in response to the catastrophic effects of the COVID-19 pandemic. Several studies have been fielded to understand the mystical vaccine’s impacts on the human body. 

For instance, a recent study at the University of Arizona affirmed that the COVID-19 vaccine does not impair the body’s physiological response to exercise. They noted that there were no changes to oxygen consumption levels or the release of certain metabolites (such as lactic acid) into the blood during exercise. It also interestingly noted that the levels of stress hormone norepinephrine were increased in vaccinated individuals as compared to unvaccinated subjects.

Similarly, extensive studies have also been done to bargain a correlation between the vaccine and allergies or other systemic conditions. Despite this colossal index of research on various culprits of human malaise, not much is talked about regarding the vaccine’s role in menstruation.

The anecdotes

According to the UK’s Medicines and Healthcare Products Regulatory Agency (MHRA), common side effects of the COVID-19 vaccine include a sore arm, fever, fatigue, and myalgia or muscle pains. They do not mention any changes to periods and unexpected vaginal bleeding.

But many primary care clinicians and those working in the scope of reproductive health have been seeing increasing reports from people who claim to have experienced such events shortly after vaccination.

In fact, the MHRA’s yellow card surveillance scheme saw more than 30,000 reports of these events by 2 September 2021. So, why is this prominent issue being swept under the rug? Or is there no evidence to prove its legitimacy?

If we are to go by what the WHO reassured us, women are encouraged to receive a vaccine at any point in their menstrual cycle with no elicited side effects. But how can so many women be wrong? Let’s look into the facts.

Correlation between COVID-19 vaccine and menstruation

After months of sifting through anecdotal claims that link the vaccine to substantial changes in the menstrual cycle, we finally have answers. A recent study did, in fact, find that the COVID-19 vaccination could potentially result in some changes to your menstrual cycle. However, before you lose sleep over this essentially harmless fact, note that the changes are likely to be relatively small and temporary.

Let us now get into the nitty-gritty of this revolutionary study.

What was this study?

A team of researchers led by Dr Alison Edelman of Oregan Health & Science University conducted this study. It was published in Obstetrics & Gynecology and funded by the National Institute of Health’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) and Office of Research on Women’s Health.

The results were reported on January 5, 2022, so this study is fairly recent.

What did the study explore?

Dr Alison Edelman and his team ventured out to see whether COVID-19 vaccines could potentially cause changes to menstrual cycles. They compared menstrual cycle length (time between bleeding) and menses (days of bleeding) in vaccinated and unvaccinated women.

What did the study do?

The study was quite simple. They analysed the data from thousands of women who regularly recorded details about their menstrual cycles using a fertility tracking app called Natural Cycles.

A total of 3,959 women took part in this study out of which 2,403 were vaccinated and 1,556 were unvaccinated. Most of the vaccinated women received either the Pfizer or Moderna vaccines.

They analysed the data from 3 consecutive cycles before vaccination, and from 3 afterwards. This also included the cycle or cycles in which the vaccinations took place. For the unvaccinated women, they retrieved the data for 6 consecutive cycles.

What did they find?

They found that women who received one dose of the vaccine during a single menstrual cycle had a small increase in cycle length. This was mostly just over half a day, on average.

On the other hand, those who received two vaccine doses within the same menstrual cycle experienced a slightly longer increase in cycle length. This was equivalent to two days, on average. However, interestingly, about 10% of these women experienced a bigger change in cycle length of 8 days or more.

These changes were only transient, which meant that they went back to normal during the following cycles. Finally, they did not find any difference in the number of days women bled for.

Dr Edelman confirmed saying, “It’s reassuring that it’s small.” There you have it, straight from the horse’s mouth!

What does this mean?

It is normal for women’s menstrual cycles to vary a small amount from month to month. The researchers pointed out that the increase they observed was “well within the range of normal variability” - a fancy way of saying, it is completely normal. All the medical jargon aside, we finally learn that the slight change in period length is nothing to be worried about.

The takeaway

We are in the midst of the largest vaccine roll-out ever seen. In the U.S., 544 million doses have been administered to date, with 79.2 million in Canada, and 139 million doses in the U.K. The COVID-19 vaccine has been recommended for all women, regardless of reproductive viability. Pregnant ladies have been widely encouraged to get the jab because it helps reduce the risk of getting severely ill from the virus and protects both the mother and the child during pregnancy.

However, one of the major reasons why many women haven’t signed up to receive the COVID-19 vaccine is that they’re worried there might be some unknown side effects of the vaccine especially on their menstrual health. However, this study demystifies the effects of the vaccine on periods. We, therefore, encourage all women to receive the vaccine to help mitigate this unrelenting problem and help put a stop to this pandemic. Period!


1.     Obstetrics & Gynecology, “Association Between Menstrual Cycle Length and Coronavirus Disease 2019 (COVID-19) Vaccination” -

2.     National Institutes of Health, “COVID-19 vaccines linked to small increase in menstrual cycle length” -

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