There has been a lot of uncertainty surrounding the side effects of the COVID-19 vaccine. Some people have expressed flu-like symptoms after getting their dose while others haven’t felt a thing. Similarly, some women have found that their periods following the shot have been different. While experts around the world have been in agreement that the vaccine should not cause any long term changes to your menstrual cycle, there may be short term fluctuations causing heavy or painful periods.

COVID-19 Vaccine and Periods

Our bodies are beautiful, constantly working hard behind the scenes to make sure we are strong and healthy. A big part of this function is dependent on the immune system. Immune cells are present in almost every part of our bodies, including the womb lining. They play a big part in building up, maintaining and breaking down the lining of the uterus. Which means if there are any changes affecting the immune cells, our cycles are also likely to be affected. 

We rely on the vaccine to cause changes to our immune system to make us resilient to the virus. However, when there are so many chemical signals, it’s possible for the immune cells in our bodies to be affected, including the ones in the womb. 

COVID-19 Vaccine and Pregnant Women

During pregnancy there are different processes in place maintaining the womb lining like the placenta, so please don’t get freaked out about the immune cells in the womb! 

There is now extensive evidence of women getting vaccinated during their pregnancy to support that the vaccine does not pose a higher risk of pregnancy loss. Pregnant women, if they want, should be offered the vaccine. COVID-19, if contracted during pregnancy can lead to preterm delivery. 


Overall, the effects on women’s menstrual cycles after the COVID-19 vaccine are temporary and there are no long-term side effects. To manage any irregular bleeding or spotting after the dose, use Friday Undies! 

About Friday Undies

Friday Undies is a period underwear brand, designed to give women comfort and confidence on their most vulnerable days. We offer an eco-friendly and reusable option for periods that is not only better for the environment but also a more comfortable and superior choice for women.