Do the mRNA vaccines cause infertility?

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.

So far, we know in the Pfizer-BioNTech trial, 23 women became pregnant. Twelve individuals received thevaccine, and 11 received placebo. No unsolicited adverse pregnancy-related events occurred. In the Moderna trial, 13 pregnancies were reported through December 2, 2020; 6 participants received the vaccine, and 7 the placebo. Two pregnancy-related adverse events occurred, both in the placebo group: one was an elective abortion, and one was a spontaneous abortion.

In addition, the COVID-19 virus itself has not appeared to affect female fertility. In a recent WebMD interview, Dr. Paul Offit, Director of the Vaccine Education Center at Children’s Hospital of Philadelphia, no evidence that this pandemic has changed fertility patterns…” and “If natural infection doesn’t alter fertility, why would a vaccine do it?”

In December, The American Society of Reproductive Medicine COVID-19 Task Force issued a statement which included the following statements.

  • The Task Force does not recommend withholding the vaccine from patients who are planning to conceive, who are currently pregnant, or who are lactating.
  • Patients undergoing fertility treatment and pregnant patients should be encouraged to receive vaccination based on eligibility criteria. Since the vaccine is not a live virus, there is no reason to delay pregnancy attempts because of vaccination administration or to defer treatment until the second dose has been administered.
  • Because COVID-19 mRNA vaccines are not composed of live virus, they are not thought to cause an increased risk of infertility, first or second trimester loss, stillbirth, or congenital anomalies.

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.


Reviewed (No Change): February 9, 2021