Does the COVID-19 vaccine really affect your period?

June 10 2020 | Written by Rhea Kumar (She/Her)

It’s jab season, folks. 

Let’s not get too far down the rabbit hole with talks of symptoms and side effects. After all, we only have one blog post. But, in the spirit of being a writer for a menstrual health company, it makes sense to get to the big red question mark: does the vaccine affect one’s period? 

We covered this topic as an instalment on our Instagram Myth Buster series, and the internet is abounding with Reddit forums, Twitter threads (see below!) but let’s find out what some medical professionals are saying.

Dr. Jen Gunter, a Canadian-American OB/GYN and author of The Vagina Bible, wrote an insightful article on The Vajenda about the COVID-19 vaccine and its connection to menstrual irregularities, but before you twitch your eyebrows and say, “Ah-ha! I knew it!” Let's get one thing clear: it’s too early to tell. And we can be pretty sure there’s not a significant risk of serious side effects like miscarriages or infertility. Before moving on, we want to stress one thing: getting vaccinated is the best way to protect yourself against COVID-19.

Alright, let’s get back to business. Most literature on this topic is purely anecdotal, which is kind of disheartening, because shouldn’t the onset of menstrual irregularities be tracked just as thoroughly as a post-vaccine fever? Gunter’s article mentions that the downstream effects like miscarriages and infertility are well tracked in most vaccine studies. So, this leaves us with a tiny suspicion that perhaps menstrual irregularities aren’t perceived as important enough to research. 

Okay fine, let’s give the researchers some credit here. After all, they did create life saving vaccines at lightning speed! But seriously, where’s the data? We conducted a small poll to ask our Instagram followers their experiences pre-vaccine and post-vaccine to get a clearer idea.

Disclaimer: Any menstrual irregularities after the vaccine does not suggest that the vaccine was the cause, and could be merely a correlation. Correlation does not equal causation, and everyone’s bodies are different!

How long did these changes in cycle last? 

While most reported that menstrual irregularities lasted for 2 cycles, our following is predominantly Canadian, and have probably only received their vaccines in the past 1-2 months. These changes could last longer, but we don’t have all the data to know yet!

Why does the Covid vaccine affect periods?

Dr. Gunter’s article touched on the multiple theories that could explain the relationship between menstrual irregularities and the COVID-19 vaccine. Such theories include that the vaccine could impact chemical messaging from the brain to the ovaries, that it could affect chemical messaging from the ovaries to the uterus, or that it could directly affect the uterus lining. However, another explanation could be that these effects are caused by one’s immune response to the vaccine as well. (Anyone else afraid of needles and totally panicked about it the night before?)

Gunter’s best guess is that any changes to one’s period is probably because of the connection between the lining of the uterus (the endometrium) and the immune system. And, as your immune system responds to the vaccine, so, in turn, would your endometrium, thus affecting your cycle.

A challenge with this sort of data is that we can be biased in noticing changes to our periods. If you’re already worried about the vaccine changing your cycle, you may pay more attention to your cycle than normal, and focus on changes that you’d otherwise ignore outside of jab season.

Despite this, Gunter’s chief point is that the lack of information and data surrounding common vaccines and menstruation is outright disappointing. Potential side effects of vaccines should be researched equally. If, perhaps, menstrual side effects were studied more, then a lot of menstruators would be questioning much less, the same way that they do when they experience a common side effect like fever or headache. This is the approach that Dr. Gunter suggests menstruators take in the event that they are experiencing some irregularities in their cycle. Headaches, joint pains and fevers are not permanent effects of the vaccine, and neither are changes to one’s period. 

Moral of the story: get vaccinated! 

P.s. if you have gotten the jab and are interested in contributing to data collection on menstrual experiences with Covid-19 vaccines, check out and consider participating in this study!