Menstrual calendar with COVID-19 viruses, vaccine bottles, period blood drops, and a used period pad

You might have heard reports of people experiencing period changes after getting the COVID-19 vaccine, or even after contracting Coronavirus. And perhaps you’re wondering if the vaccine will affect your menstrual cycle too. Well, it’s time to sort the myths from the facts.

The global pandemic has touched almost every part of our lives. We’ve experienced so many changes – from how we work, travel and socialise, to how we think about our bodies, our health and even our menstrual cycles.

And changes don’t come without their share of stress, which is one of the factors that can affect periods. [1] This is just one explanation of why you may have noticed some changes to your menstrual cycle during the pandemic – and you’re not alone, it’s been a pretty stressful time for all of us! [2]

But could another explanation be related to the vaccine or getting the COVID-19 virus? And is there anything you should do about it? Let’s look into the facts…

The lowdown on the COVID-19 vaccine and your period

As vaccines were rolled out all over the world, reports started to circulate that some people were noticing changes to their menstrual cycle or having unexpected bleeding after getting jabbed. You might have heard your friends or family mention that their menstrual calendar was a bit off, or you may even have spotted it yourself. Well, more than 36,000 people made reports of this in the UK at the beginning of 2022 [3] and similar reports in the US led to the National Institute of Health funding studies to work out if there are any potential effects of COVID-19 vaccination on menstruation. [4]

Can the vaccine delay your period?

A study from the US [5] found that while the first dose of the vaccine had no effect on the timing of someone’s next period, a second dose was related to an average delay of less than 6 hours – which might be barely noticeable for most of us! It also discovered that people who received two doses of the vaccine within the same menstrual cycle, got their period delayed by roughly 2 days. And just over 10% of this group experienced a change in length of more than 8 days.

Not only were the delays quite short, but the study also found that periods returned to their usual timing just two menstrual cycles after being vaccinated. So while these changes may be less than ideal (it can be tricky to track our cycles as it is!), keep in mind that they won’t last forever. It’s also totally normal to experience irregular or late periods at many points during our life, so try not to worry.

Can you get period pain or heavy periods after the vaccine?

A study from the Norwegian Institute of Public Health [6] looked into menstrual changes such as worse than normal period pain both before and after having the vaccine. They found that heavier than normal bleeding was the most frequently reported symptom after getting the COVID-19 vaccination. After having the second dose of the vaccine, they found that there was also a higher chance of experiencing symptoms like prolonged flow, shorter or longer time between periods, more painful periods, period-like pains without flow, and even unexpected breakthrough bleeding (bleeding that isn’t your period).

However, the study also revealed that around 38% of participants noticed at least one change to their cycle even before getting jabbed, which shows that menstrual cycle changes are completely normal anyhow.

If you do find that your flow is heavier than usual (for whatever reason), you may consider using a high absorbency period pad or period pants designed for heavier flow. This can help you feel more protected and comfortable!

So what do these studies show about the vaccine and menstruation?

Overall, both studies are reassuring, and can help us feel a little more relaxed about getting the vaccine. They show that it’s normal to experience changes to our menstrual cycle or period after getting jabbed, but also that these changes are small, and similar to the usual variations we all experience throughout life. They also quickly reverse, so within a couple of cycles’ time everything is back to what’s normal for our bodies.

Why does the vaccine affect your menstrual cycle?

As we’re still in the early days of research into the relationship between the COVID-19 vaccine and menstrual cycles, it’s difficult to be sure of what might exactly cause these effects. We’re all different, so it may even vary from person to person!

What we do know is that the brain, ovaries and womb work together to make menstrual cycles happen. So it could be that the vaccine temporarily affects the part of our brains that controls hormones, which would in turn have an impact on when our ovaries release an egg or how the lining of our wombs is shed during a period. [1]

It could also be explained by how vaccines work to trigger a response from our immune system to protect us from future infection.

Imagine the vaccine like a training course for soldier cells inside your body that teaches them how to fight off an attack from the Coronavirus. These soldiers (your immune system) are stationed in various positions all around your body, ready to defend it. This includes in your uterus lining (known as the endometrium). Such intense training for the cells due to the vaccine could cause inflammation that results in a heavier or irregular period. [7]

Will the vaccine affect birth control, fertility, or my ability to get pregnant?

Reports of women+ experiencing changes to their menstrual cycle after receiving the vaccine have come from both those who use hormonal birth control and those who don’t. And there has been no indication that getting jabbed will change how effective your hormonal contraception is. [1] However, if you do have any concerns, it’s best to make an appointment with your doctor who will be able to offer personalized advice.

On the other hand, there is no evidence that vaccine-related temporary changes to the menstrual cycle have any impact whatsoever on someone’s fertility or ability to get pregnant at a later date. [1] So this concern shouldn’t prevent you from getting jabbed. If you’re planning to have a baby, it is actually a pretty good idea to get the vaccine, as unvaccinated pregnant women have a higher risk of becoming seriously ill due to COVID-19. [1]

Can Coronavirus infection affect your menstrual cycle?

If you catch Coronavirus, your menstrual cycle may be the last thing on your mind. However, there is some evidence that it can get affected. A study in a hospital in China [8] looking into menstruating COVID-19 patients found that 20% had lighter periods or longer cycles than usual. They explained this as a result of hormonal changes triggered by the virus messing with the normal function of the ovaries. However, the good news is that their menstrual cycles went back to normal after recovery.

Although getting sick can be inconvenient and even scary, knowing that these side effects are brief can be reassuring. So if you do find yourself infected with COVID-19, try to focus on looking after yourself and resting until you feel better and are no longer infectious.

What should you do if experiencing period problems after the COVID-19 vaccine?

If you notice any subtle changes to your menstrual cycle after having the vaccine, remember that it’s normal. If the jab is the culprit, then your period should get back on track very soon.

However, when that doesn’t happen after a couple of months and you’re starting to worry, you may want to reach out to your doctor. Also, if you experience any heavy bleeding that is unusual for you, especially if you’ve gone through menopause, it’s a good idea to speak to a healthcare professional to get to the bottom of it. [1]

Overall, the available research on how COVID-19 and the vaccine can affect your menstrual cycle is a bit limited but still reassuring. Any changes in your cycle are to be expected and wear off over time, so try to be patient and give your body the time it needs to adjust. [9] And if you have any lingering worries or questions, it doesn’t hurt to contact your gynaecologist... it’s their job to help you, after all!

If you’d like to get clued up about all things menstrual cycle, you may like to find out more about stress and periods or how hormones affect you.

Medical disclaimer

The medical information in this article is provided as an information resource only, and is not to be used or relied on for any diagnostic or treatment purposes. Please consult your doctor for guidance about a specific medical condition.




[3]  Medicine and Healthcare Products Regulatory Agency. Coronavirus vaccine—weekly summary of Yellow Card reporting. 13 Jan 2022.

[4]  Eunice Kennedy Shriver National Institute of Child Health and Human Development. Item of interest: NIH funds studies to assess potential effects of COVID-19 vaccination on menstruation. 2021.

[5]  Edelman A, Boniface ER, Benhar E, et al. Association between menstrual cycle length and coronavirus disease 2019 (covid-19) vaccination: a US cohort. Obstet Gynecol2022. doi:10.1097/AOG.0000000000004695 pmid:34991109

[6]  Tragostad L. Increased occurrence of menstrual disturbances in 18- to 30-year-old women after covid-19 vaccination. [Preprint.] SSRN 2022. doi:10.2139/ssrn.3998180




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