A range of period products lie against a pink background. To the left there are white sanitary towels with blue daisies printed on them, with tampons and sanitary towels on the right hand side.

Blood, jabs and tears: the undisclosed menstrual side effects of the covid-19 vaccine

By Melisa Korkut

Melisa Korkut discusses the reported period changes following the Covid-19 vaccine.

In recent months, claims of people noticing changes to their periods after receiving the Covid-19 vaccine have emerged on social media. This likely came as such a shock because the possibility of menstruation changes as a side effect is not included in the patient aftercare leaflet, nor does the vaccination nurse mention it at the time. This raises the question of why people who menstruate have been left to think that they are alone in seeing confusing and worrying changes to their bodies.

“The possibility of menstruation changes as a side effect is not included in the patient aftercare leaflet…”

I’d consider myself quite the hypochondriac; I like to know exactly what my symptoms mean, why I have them and when they’ll go away. I’ve never felt like I had a strong awareness of my body and have a history of erratic periods where stress and anxiety left me without a period for over a year. Personally, anything about my health that can be explained and normalised is a huge reassurance to my mental wellbeing. I was fortunate to not see any changes to my period after I received the Moderna vaccine. However, as someone who would have been extremely anxious in that situation, I wanted to know how those who did see changes felt about it all. I reached out via Instagram stories to ask if any of my friends had experienced this issue. One respondent had similar feelings to me over how period woes can affect us mentally:

“I experienced the worst and longest period of my life… knowing about these period-related changes beforehand would have eased a lot of my anxiety as to what caused such a bad experience… I already had reproductive worries and not knowing this side effect really distressed me mentally, as I thought my body was attacking itself and I believed my experience to be completely abnormal… even family members thought I was overreacting.”

Another respondent was concerned over these changes as she and her partner are trying for a baby:

“As a TTC (Trying To Conceive) gal who has suffered an ectopic pregnancy, it is important that I feel I know what is going on inside my body, and I think many women feel the same… I was left worrying how long I’d wait for my period to show and would it ever be “normal” again, would it affect my fertility?”

Do these side effects line up scientifically? According to a reproductive immunologist interviewed by the BBC, vaccines trigger a plethora of chemical signals which can affect immune cells circulating around the body, causing the womb lining to shed, leading to heavier bleeding. Sounds reasonable enough, and much less scary. But it would have been great to know this before it happened to so many of us.  

“Vaccines trigger a plethora of chemical signals which can affect immune cells circulating around the body, causing the womb lining to shed…”

This issue highlights a recurring theme of clinical trials failing to look into possible period-based side effects, as stories like these are unfortunately not uncommon when we consider the history of other vaccines. The HPV (human papilloma virus) vaccine, which has been rolled out in the UK to girls aged 12-13 since 2008, has also been associated with period changes, yet again there has been little demand for research to explain this. Since there is no data collected on menstruation changes, participants in trials usually have to note them down vaguely as “adverse events”. Pfizer and Moderna have claimed that the majority of trial participants experienced no menstrual changes, yet out of the four people I spoke with, two had Moderna, another Pfizer and one Oxford, and they all saw period changes. If it appears to be seen with several different vaccines, shouldn’t this be even more reason to disclose menstrual changes as a possibility? 

The fact that it isn’t discussed could be down to the sadly still innate taboo surrounding periods. One of my respondents agreed, adding that the Covid vaccines complicated things: 

“I think post-vaccine side effects are difficult to talk about without coming across as an anti-vaxxer, which I’m definitely not.  Mix that with the general taboo around menstruation and women’s bodies, and it becomes very hard for these topics to be brought up.”

Rather than contributing to vaccine hesitancy among people who menstruate, preparing them for this eventuality can assure them that information about their health is being fully disclosed to them, with the potential added bonus of providing anti-vaxxers with less grounding for their claims that we don’t know how the vaccine will affect our bodies. The last thing we want is more reason for people, particularly those who are predisposed to distrust vaccines, to not be aware of the full picture, however seemingly unlikely the side effects may be.


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