COVID vaccines effects on fertility and pregnancy

by Guy Ringler, MDMarch 29th, 2021

While we have some clinical answers about the effects on male and female fertility, we have fewer conclusions about pregnancy.

As COVID vaccines roll out around the world, men and women looking to conceive are wondering how they might affect fertility.

The truth is, because the vaccines are so new, we have some answers but we don’t have all of them.

Three vaccines in the United States

Over the last few months, two companies in the U.S. – Pfizer-BioNtech and Moderna – initially introduced vaccines to the public that have been shown to prevent severe disease in up to 95% of patients. These vaccines require two shots, about four weeks apart.

These vaccines are composed of messenger RNA (mRNA) that encodes a portion of the spike protein present on the surface of the coronavirus. Once injected into our arms, the mRNA molecule gives muscle cells instructions to make a portion of the spike protein. These spike proteins are then recognized by our immune cells, and that triggers the production of antibodies that attack the virus and prevent its replication.

In addition, a vaccine from Johnson & Johnson -- known as the Janssen vaccine -- has been approved for emergency use and is being delivered across the country. The Janssen vaccine is only one shot.

Unlike the other two vaccines that use mRNA, the Janssen vaccine, according to Johnson & Johnson, uses an “adenovirus—a type of virus that causes the common cold—that has been made unable to replicate” and carries a gene from the coronavirus. That triggers the same immune response as the other two vaccines.

So what does that all mean for people looking to get pregnant, or who are already pregnant?

Effects on fertility

The mRNA COVID vaccines have been tested in clinical studies and have not been shown to cause infertility in women or men. A similar number of patients conceived following injection of the Pfizer vaccine as those that received the placebo. In addition, a study with the Moderna vaccine did not show any impact on fertility in rats.

Some Internet posts have expressed concern that the vaccine might interfere with placenta formation, since the mRNA molecule shares a very small segment of genetic code for a protein that helps build the placenta, but the COVID vaccine does not induce antibodies against this protein.

Johns Hopkins Univ. recently called the notion that the vaccines can have an effect on a woman’s fertility a “myth,” highlighting this from two experts:

“The COVID-19 vaccine will not affect fertility. The truth is that the COVID-19 vaccine encourages the body to create copies of the spike protein found on the coronavirus’s surface. This ‘teaches’ the body’s immune system to fight the virus that has that specific spike protein on it.”

It should be noted, however, that we don’t have fertility-study results with the Janssen vaccine, so we can’t make any firm conclusions at this time. However, because it does not utilize mRNA, the internet rumors about infertility that followed the other two vaccines have not been widespread.

Effects during pregnancy

Clinical studies on the COVID vaccines during pregnancy have not yet been conducted. Various groups including the CDC have said the vaccine should be offered to pregnant women, as it is not believed to have an effect and there are so far no reports of the vaccine ending a pregnancy amongst pregnant women who have taken it.

When considering whether to receive the vaccine, pregnant women should compare the potential risks of the vaccine to the risks of acquiring COVID while pregnant.

Reports have identified potential risks of COVID infection during pregnancy to include: greater severity of infection of the disease, more hospital admissions, and increased risk for early delivery compared to non-pregnant women.

As the incidence of COVID within communities changes around the world, one must reassess and weigh the risks of acquiring the infection in your area versus the potential risks of getting the vaccine.

For women who are trying to conceive, or who are pregnant, several professional organizations have recommended that women receive the vaccine after considering the risks and benefits of the injection. The CDC, the American College of Ob/Gyn, and the Society for Maternal and Fetal Medicine have all recommended that the vaccine not be withheld from this group of women since, for most women, the benefits of the vaccine outweigh the risks.

But to be clear, we do not have conclusive information about the effects of the vaccines on a pregnancy at this time.

One positive sign has been recent studies that show a vaccinated pregnant woman passes COVID antibodies to her baby in utero and through breastmilk, though it should be noted this is for the mRNA vaccines.

It’s important to discuss with your doctor / fertility specialist whether the vaccine is in your best interest and the timing of your vaccination.

We are working with colleagues and specialists across North America and Europe to continue to ensure the safety of family-building, and we will update this post as we receive more information.

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