LATEST UPDATE: 30-10-2022

Delayed periods. Spotting. Heavier bleeding. Suddenly menstruating again even though you thought menopause has already come and gone. And all of that just after you were vaccinated against corona… Coincidence or not? More and more studies show temporary changes in the menstrual cycle. Researchers say that people should be aware of the fact that it can happen, but that it’s too early to draw conclusions. The latest and largest study to date, based on data from 39,000 people, was published July 15 in Science Advances. October 28 the  committee recommended adding heavy menstrual bleeding to the list of side effects of mRNA COVID-19 vaccines made by Moderna, Pfizer and BioNTech.

– BY YAYERI VAN BAARSEN –

In the last few years, thousands of women worldwide have reported changes in their menstrual cycle after being vaccinated against Covid-19. Up until 29 June 2022, the UK’s Medicines and Healthcare Products Regulatory Agency (MHRA) has already received 39,986 notifications. In these so-called Yellow Card reports, a total of 51,321 suspected reactions relating to a variety of menstrual disorders have been named, including heavier periods, delayed periods and unexpected vaginal bleeding. (One report can contain more than one suspected reaction). In the Netherlands, Lareb, Knowledge Centre for adverse drugs reactions (ADRs), has received 24,090 reports about post-vaccine menstrual irregularities (of a total of about 17 million vaccins given to women) up until 29 March 2022. There’s a wide variety in complaints, but generally women indicate that menstruation after vaccination is different than before.

Most reported: heavier periods

Most of the Lareb reports were about heavy periods (7635 times) and delayed periods or not menstruating anymore (together 8100 times), followed by irregular periods and spotting. In follow-up questions, most women who reported heavy periods mentioned a heavier menstrual flow of more than twice as much. According to Lareb, it’s still too early to say whether a disrupted cycle is really a side effect of the corona vaccines; for this, more research is needed. However, they state, ‘The vast amount of spontaneous reports and the relatively high frequency from the cohort study indicate that there is a possible causal relationship between COVID-19 vaccination and menstrual disorders.’

Also the European Medicines Agency (EMA), which started a thorough analysis of all European reports, data and literature, in February 2022 is still investigating a possible link between the vaccine and heavy periods. On June 10, the the Pharmacovigilance Risk Assessment Committee (PRAC) of the EMA already concluded there’s no causal association between mRNA Covid-19 vaccines and amenorrhea (the absence of menstruation). Latest update: now the EMA committee recommendeds adding heavy menstrual bleeding to the list of side effect of mRNA COVID-19 vaccines made by Moderna (MRNA.O), as well as Pfizer (PFE.N) and its partner BioNTech (22UAy.DE).

The latest study – the largest to date, published July 15 in Science Advances – shows that 42% of people with regular menstrual cycles experienced heavy menstrual bleeding after vaccination, while 44% reported no change and 14% reported lighter periods.  In addition, 66% of postmenopausal women experienced a breakthrough bleeding after one or more vaccinations. The study compared data from more than 39,000 people (including trans men and postmenopausal women) who had been vaccinated twice against Covid-19.

‘I think it’s important that people know this can happen, so they’re not scared, they’re not shocked and they’re not caught without supplies,’ said Katharine Lee, biological anthropologist at the Washington University School of Medicine in St. Louis in New York Times. She cautioned, however, that the study didn’t compare the results with a control group of people who didn’t get vaccinated. It’s also possible that people who observed changes in their cycles after vaccination may have been more likely to participate in the survey. Still, the findings line up with smaller studies that have reported menstrual changes after vaccination with more robust controls.

Cycle changes? Stress can also be a reason

What’s going on? First things first: it might sound strange with all these studies, but a link between corona vaccines and menstrual changes still hasn’t been proved yet. Cycle changes can have all sorts of reasons. Often, it’s because of stress, but also another diet, more or less exercise and of course a medical condition can disrupt things. Your periods change anyway during your life: especially in the years just after the menarche and in the premenopause women often menstruate heavier and irregular.

Added to that: a chronological connection doesn’t automatically mean a causal connection. If you get sunburned the day after your vaccine, perhaps not the jab is to blame, but the fact you’ve spent the entire afternoon in the sun without putting on sunscreen. In other words: the heavier periods and spotting after the vaccine could also be caused by stress, fibroids, or being premenopausal. Talking about stress: the corona pandemic has disrupted the daily lives of many people.

Immune system is linked to your hormonal system

On the other hand it seems like there actually is a link between corona vaccines and menstrual disruptions. More than 30,000 women in the UK who all experience cycle changes directly after getting the jab, without this being linked to the vaccine? Seems a bit too much of a coincidence. As mentioned above, this isn’t only happening in the UK. In the Netherlands, there have already been almost 17,000 reports of menstrual disruptions after Covid-vaccine and in the United States, the number has risen to over 140,000 cases. (Numbers from November 2021). A more recent Norwegian study among nearly 4,000 women also showed increased incidence of menstrual changes after vaccination.

How can this be explained? Put simply, a vaccine triggers an immune respons within the body. Your immune system and your hormonal system (also called endocrine system) are inextricably linked. Your hormones regulate your menstruation and the uterus lining (which is shed during menstruation) contains immune cells. Heavier periods could thus be part of the body’s normal immune reaction to a vaccin.

Known vaccination side effects, like fever, can also impact your cycle. This isn’t just the case with Covid-19 vaccines, but also with side effects of flu shots or the HPV-vaccine. Menstrual disruptions have been reported after both the adenovirus vectored covid-19 vaccines (AstraZeneca and Janssen) and the mRNA-vaccins (Moderna and BioNTech/Pfizer). This also points towards the complaints being related to the entire immune system instead of related to certain ingredients of a specific vaccine. Lareb, the Dutch Knowledge Centre for adverse drugs reactions, states: ‘The vaccine stimulates the immune system and this could possibly influence the hormone levels.’

‘Dose 1 of Moderna … and am gushing like I’m in my 20s again’ – Kate Clancy

One of the first who brought this to the attention, was the American Kate Clancy. In February 2021, she tweeted about her heavy post-vaccine menstruation: ‘I’m a week and a half out from dose 1 of Moderna, got my period maybe a day or so early, and am gushing like I’m in my 20s again’. The respons was overwhelming. Together with researcher Katharina Lee, Clancy, associate professor of anthropology at the University of Illinois, set up an online survey to document this phenomenon. Clancy’s tweet led to hundreds of thousands of women sharing their experiences.

In September 2021, BMJ published an article by Victoria Male, lecturer in reproductive immunology, which talks about the situation in the UK. There, over 30,000 reports about a disrupted cycle and unexpected vaginal bleeding have been filed via the Medicines and Healthcare Products Regulatory Agency’s (MHRA) yellow card surveillance scheme for adverse drug reactions. Despite that, the MHRA claims that evaluation of these reports ‘does not support a link between changes to menstrual periods and covid-19 vaccines’. The main message of Male’s article: a link between vaccines and menstrual changes is plausible and should be investigated.

1.67 million dollar for American research

The US National Institutes of Health (NIH) has awarded 1,67 million dollar (1,2 million pound) for further research. These funds will be used by five American institutions: Boston University (principal investigator: Lauren A. Wise, Sc.D), Harvard Medical School in Belmont, Massachusetts (principal investigator: Laura Allen Payne, Ph.D.), Johns Hopkins University in Baltimore (principal investigator: Mostafa Borahay, Ph.D.), Michigan State University in East Lansing (principal investigator: Stacey Ann Missmer, Sc.D.) and Oregon Health and Science University in Portland (principal investigator: Alison B. Edelman, M.D.).

The researchers will study the potential effects of the Covid-19 vaccinations on the menstrual cycle. For this, they’ll be looking at post-vaccination changes to flow, cycle length, pain and other symptoms. They’ll also study how long these menstrual changes last and which mechanisms are causing them. One of the studies will focus on adolescents.

In The Netherlands, Lareb will study the reports and investigate the complaints. Up until February 2022 they received 699 reports of bleeding after menopause. Seeing as in over half of the women this bleeding started within two weeks after vaccination, Lareb will now research how many women have visited their GP with these complaints before and after getting vaccinated. ‘There are quite a lot of reports, and they are also striking in the sense that women say they’re now suddenly suffering from a menstrual disorder. We therefore think it is indeed possible that menstrual disorders are a side effect,’ Lareb director Agnes Kant already told the Dutch broadcaster NOS Nieuws on 22 December 2021.

Also in Spain, where a preliminary survey of 14,000 women showed that 70% experienced menstrual changes after vaccination, a scientific study is underway. The EVA project, carried out by the Biosanitary Research Institute of Granada University and the San Cecilio University Hospital of Granada and led by professor Laura Baena, will follow just over 100 women for a year. This project aims to charactarise any post-vaccine menstrual disorders and do blood tests in order to study the biological mechanism that could be involved.

Wake up call for science?

Currently, women who get vaccinated aren’t warned for any menstrual disruptions as a possible reaction to the jab. First, studies will have to show if there truly is a link. Perhaps in the future, heavy periods will be mentioned alongside other side effects such as fever, headache, and tiredness. In the meantime, this could be a good wake up call for science. Hopefully from now on, the menstrual cycle won’t be disregarded completely when developing vaccines and/or medicines, like it’s been up until recently in nearly all medical scientific research.

Good news for all the women who hate their unexpected and/or heavier periods and are desperately looking for sanitary pads size XL: doctors claim the cycle changes are short-term and aren’t dangerous. Most women will return to their normal pattern within a couple of months. Trying to get pregnant? There are no indications that corona vaccines can cause infertility, says Lareb.

We’ll keep you informed. Period!

LATEST UPDATE: 30-10-2022

Image: Shutterstock.

Period! is an independent, online magazine about all aspects of menstruation. Period! is not intended as a substitute for medical advice. If you’re suffering from medical complaints, always visit your doctor or GP. Editorial articles can contain affiliate links. Sponsored collaborations can be found in the category Spotlight. Do you have any questions? Check our Contact page.

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