Fertility & Menstruation

Can COVID-19 vaccines cause infertility?

No. Getting the COVID-19 vaccine will not affect your fertility – and there is no reason to delay pregnancy upon receiving the vaccine, as it does not contain any ingredient that could lead to fertility issues among men or women. 

This false claim is based on a blog post circulated in December of 2020 that claimed the vaccine could cause the body to attack syncytin-1, a protein in the placenta that shares a small piece of genetic code with the spike protein of the coronavirus. 

While similar, these two proteins are not the same. It’s like comparing oranges to lemons—they’re both citrus fruits, yes, but if you plant a lemon seed you won’t be growing an orange tree. Studies have all shown no significant relationship between the vaccine and fertility issues [1]. This includes relationships to miscarriage and sperm counts [2,3].  Although there might be the one small similarity, the overall structure of the protein is completely different, and your immune system is way too smart to be confused by that.

What can affect your menstrual cycle:

  • Stress
  • Illness
  • Lifestyle changes

Can vaccination permanently affect menstruation?

In short, no! The menstrual cycle is itself a cycle of immunity. The immune system is suppressed during ovulation to allow sperm to enter. It then kicks in again in order to shed the lining of the uterus. 

While some women have noted a change in their menstrual cycle after vaccination, these changes can be explained by a number of different factors including stress, illness, or lifestyle changes. The COVID-19 vaccination has not been found to have any direct link to changes in menstrual cycles, and doctors and scientists do not see any physiological reason for this to occur, and the evidence around abnormal periods is so far purely anecdotal [4,5].

Ultimately, menstrual health can be a reflection of one’s overall health, and periods, including length and flow of a menstrual cycle, vary widely from person to person.  Vaccines are safe, effective and necessary to end the pandemic.

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  1. Male, V. Are COVID-19 vaccines safe in pregnancy?. Nat Rev Immunol 21, 200–201 (2021). 
  2. Cosma S, Carosso AR, Cusato J, et al. Coronavirus disease 2019 and first trimester spontaneous abortion: a case-control study of 225 pregnant patients. Am J Obstet Gynecol 2021;224:391.e1-7.
  3. Gonzalez DC, Nassau DE, Khodamoradi K, et al. Sperm Parameters Before and After COVID-19 mRNA Vaccination. JAMA. 2021;326(3):273–274. 
  4. 4.Womens Health. Cleveland Clinic. Will a COVID-19 Vaccine Throw Your Period Off? July 9, 2021. 
  5. 5.Li K, Chen G, Hou H, et al. Analysis of sex hormones and menstruation in COVID-19 women of child-bearing age. Reprod Biomed Online. 2021;42(1):260-267.