Do the mRNA vaccines cause infertility? (UPDATED*)

Female infertility

At this time, there is no evidence showing that COVID-19 vaccines causes infertility. This concern stems from information that protein called syncytin-1, which is found in the placenta in mammals, shares similar genetic instruction with part of the COVID-19 spike protein. It is postulated that if the vaccine causes the body to produce antibodies against the spike protein, it will also cause it to produce antibodies to syncytin-1, leading to infertility. Currently, there is no evidence to support this theory. Neither COVID-19 mRNA vaccines contain syncytin-1, nor does the mRNA used in the vaccines encode for syncytin-1. In addition, the spike protein formed as a result of vaccination with either COVID-19 mRNA vaccines and syncytin-1 are structurally very dissimilar. No data indicates the antibodies formed as a result of COVID-19 mRNA vaccination target syncytin-1.

In January 2021, The American Society of Reproductive Medicine COVID-19 Task Force issued a statement which included the following:

  • Available data indicate that COVID-19 vaccines do not cause infertility in women or men. 
  • In the randomized blinded Pfizer-BioNTech trial, a similar number of women conceived after receiving the vaccine as those who received the placebo. 
  • The coronavirus’s spike protein and syncytin-1 (protein that mediates placental cell fusion) share small stretches of the same genetic code but are otherwise completely different in structure. The vaccine does not induce an immune reaction against the syncytin-1 placental protein. 
  • mRNA vaccines are taken up rapidly by muscle cells at the injection site and the mRNA is degraded in the cell once the protein is made so it does not cross the placenta. 
  • COVID-19 vaccination is recommended for women who are contemplating pregnancy or who are pregnant in order to minimize risks to themselves and their pregnancy.

In July 2021, the American College of Obstetricians and Gynecologists (ACOG) updated their recommendations:

  • Claims linking COVID-19 vaccines to infertility are unfounded and have no scientific evidence supporting them. ACOG recommends vaccination for all eligible people who may consider future pregnancy.

Male infertility

In January 2021, the Society for Male Reproduction and Urology and the Society for the Study of Male Reproduction issues the following statement:

  • The COVID-19 vaccine should not be withheld from men desiring fertility who meet criteria for vaccination.
  • COVID-19 vaccines should be offered to men desiring fertility, similar to men not desiring fertility, when they meet criteria for vaccination.
  • It should be noted that about 16% of men in the Pfizer/BIoNTech COVID-19 vaccine clinical trial experienced fever after the second dose. Fevers can cause temporary declines in sperm production. Thus, if a man experiences fever as the result of the COVID-19 vaccine, he may experience a temporary decline in sperm production, but that would be similar to or less than if the individual experienced fever from developing COVID-19 or for other reasons.


Updated: August 30, 2021