I had a follow up mammogram a couple of weeks ago, and the first thing the tech asked me was if I’d had a vaccine yet. I thought she was making conversation, but it turns out that vaccines can cause inflammation in the lymph nodes, resulting in inaccurate results.
I tucked that information away, but started noticing a lot of buzz about whether there is a relationship between any of the covid vaccines and fertility (apparently a lot of healthcare providers are not getting their vaccines because “I haven’t had my family yet”), and more recently, vaccines and periods. Is this all just noise? Or is there anything to it?
First — and the most important thing — is that researchers haven’t yet really studied the relationship between the covid vaccines and the menstrual cycle. There’s a whole long patriarchal history behind this, but as this New York Times piece outlines, researchers just don’t study (or understand) menstruation well enough. But there does seem to be some increasing anecdotal suggestion that many period-having people have some disruption in their menstrual cycles following vaccination, either skipped periods, breakthrough bleeding or heavier, earlier periods. So what does that mean? Should we be worried about the intersection between vaccines and reproduction?
To try to unpack this, I turned to The Vajenda, my favourite source of gyne-related info, written by Dr Jen Gunter, an OBGYN and pain physician. (It’s a substack, so you have to subscribe, but there is a free option that gets you about half the posts.)
Here is her definitive post on the vaccine and menstruation:
Here are two related posts:
And my favourite:
The Covid-19 vaccine is a vaccine, not a spell — no, it can’t affect other people’s reproductive cycles by proxy. More on this below.
I’ll distill the key takeaways from these posts — with the most important being that even if scientists haven’t fully studied menstruation and vaccines — and they SHOULD, hello patriarchy — we can still use science to do some thoughtful and factual analysis of what might be happening.
- The point of a vaccine is to engage the immune system to teach it how to fight a foreign interloper that looks specifically like the thing you are being vaccinated for. A critical part of the immune system is lymphocytes, which produce the cells that make up the antibodies your body needs to fight to off any illness or infection. You have lymph nodes — small glands that produce and filter lymphocytes — all over your body, but very noticeably under your armpits.
- About 10 – 15% of people experience swollen lymph nodes after any vaccines, which is totally normal, because it means the immune system has received a signal that something foreign has happened and it is marshalling its little knowledge system to figure out how to respond to it.
- These swollen nodes can show up on mammograms as an irregularity, which can mess up mammogram results — so if you are going for a regular screening, try to put it off for “at least four to six weeks” after your last vaccine dose. But don’t put off scanning for any problem you might be experiencing.
The first thing Dr Gunter underlines is that there may actually be no link between vaccines and period weirdness — it may be something people are connecting because it’s happening anyway and they just happen to be paying attention to their bodies in a more heightened way, or there may be changes caused by stress. But IF there is actually an impact for some people, there are different hypotheses for why this might be true. All of them come back to the relationship between the uterus and the immune system.
I have to say, I’m pretty interested in menstruation — I’m well known around these parts for a post on menstruating well into my 50s that shows up in the top 10 almost every month — and even I did not know that there are “a lot of complex immune system interactions in the lining of the uterus that are also involved in menstruation.” In other words, your period isn’t just a thing happening out there on its own little agenda, it’s highly intertwined with all of the other things going on in your body around health and your general experience of immunity. This is why stress and fatigue and colds and other illness can affect menstruation.
Dr Gunter outlines three different mechanisms for how the vaccine could possibly interact with the menstrual cycle:
- nitric oxide, which is produced when the immune system is activated, also has a role in causing endometrial tissue breakdown — so it could accelerate a ‘normal’ cycle
- vaccines can trigger the release of inflammatory cells called “mast cells”, which also relate to the enzymes that break down the lining of the uterus
- proteins called “toll-like receptors” (Tlrs), which play an important role in regulating the essential functions of our uterus and ovaries, are also sensitive to changes in single-stranded RNA; COVID-19 is a single stranded RNA virus, and the Pfizer and Moderna are RNA vaccines.
I could go down a rabbit hole here, but the basic upshot is: menstruation is intertwined with the immune system; vaccines trigger the immune system; ergo, just as we may experience immune responses like chills, fever, fatigue, etc after a vaccine, we may very well experience effects in this menstrual part of our immune system. And as Dr Gunter underlines, actually CATCHING COVID-19 is likely to have an even more powerful impact on your menstrual cycle.
So. Don’t put off getting vaccinated because it might mess with your period: serious illness will mess with it more. Do, however, pay attention if you bleed after the vaccine after menopause — that IS something to pay attention to. And if you want to participate in the first research to track the relationship between vaccines and your period, here is a link to a brand new study:
Now, what about fertility?
First, studies have been done on the relationship between pregnancy and vaccines, with the conclusion that the COVID-19 vaccine is safe for pregnancy, not associated with miscarriage, and does not damage the placenta. And again, it’s more dangerous to actually get COVID while you’re pregnant. The province I’m in added pregnant people to the list of vaccine priorities last week because of ICU admissions for pregnant people.
I do understand anxiety about something unknown and pregnancy — someone very close to me didn’t even want general anesthetic when she had to have her appendix out during a pregnancy for fear of what it might do to the fetus. (The surgeon, appropriately, said no, she needed the anesthetic, and both she and the baby were fine.) Pregnancy can be an anxious time, and this is new. But again, the science is helpful here.
There is a full, great explainer of how vaccines work here in the New York Times. But the basic takeaway is that once either type of vaccine has done its work of teaching your immune system how to specifically respond to the spike protein on the surface of the COVID-19 virus, it disappears. It has one job, just like every other vaccine. It shows up, livens up the party, does a little dance, and leaves, leaving you with a temporary hangover.
So yes, it’s possible that the parts of your reproductive system related to the immune system might be triggered during the time you are actually responding to the vaccine — but that goes away. There is no reason whatsoever — no hint in the science, no hint in the research, no hint in the logic of how vaccines work — to think that there will be any more impact on long term fertility than any other vaccine. For more in-depth understanding, read the piece linked above in Nature — it details how the rumour about mRNA vaccines and fertility got started, and why the science completely counters it.
The final thing I want to just briefly touch on is the lunacy that people who have been vaccinated could affect the reproductive cycles of other people. There are alarming pockets of the world who believe this, including a private school in Florida that has forbidden people who’ve been vaccinated from interacting with their students. That’s just plain bonkers. As Dr Gunter wrote, it’s a vaccine, not a spell. And it’s a terrible indictment of people’s complete illiteracy about basic biology.
So the bottom line: of course I’m not going to tell anyone what to do. But if you’re hesitant, spend some time dwelling in the science. Even though these vaccines are new — we didn’t even know this virus existed 18 months ago! — the science behind them is tried and sound. Reassure yourself. And protect yourself. And everyone else.
Fieldpoppy is Cate Creede, who is an amateur immunologist. Here is her vaccine selfie, for which she is very grateful.