A new study shows vaccination against COVID-19 has no negative effect on the placenta

File this under More Good News!

Another study was published this week that adds to what we know about the safety of the COVID-19 vaccine during pregnancy. This study looked at the placentas of women who had been vaccinated and compared them with women who had not been vaccinated. They found no signs of any concerning changes related to vaccination. The placenta can provide a wealth of information about pregnancy, and so this is important new data.

We need studies like this because there is a persistent Internet rumor that vaccination against COVID-19 can somehow harm the placenta or lead to infertility. It’s worth noting that some of the biggest drivers of these lies, Dr Christiane Northrup and Dr. Naomi Wolf, have had social media accounts disabled for misinformation (Northrup from Instagram and Wolf from Twitter).

This myth about the vaccine and pregnancy appears to be based on the false belief that a protein in the placenta called syncytin-1 is similar to the spike protein found on COVID-19. As the COVID-19 vaccines tell the body to make antibodies to the spike protein, the “theory” (the word theory is doing a lot of heavy lifting here) is the antibodies generated by the vaccine could mistakenly attack the syncytin-1 protein in the placenta leading to miscarriages. The spike protein on COVID-19 and syncytin-1 are different sizes and only share 3% of the same amino acids (building blocks) so this theory was never biologically plausible. For anyone wanting a little more information, this post addresses it in more detail. 

While the theory about the spike protein and the COVID-19 vaccine is not biologically plausible, it is still important to understand if there are any issues related to the vaccine and the placenta.

Infection with COVID-19 is known to stimulate toll-like receptors, which are part of the innate immune system (our general defense system), antibodies are part of the adaptive immune system (more targeted defenses). As an aside, we’re covering the immune system in Episode 5 of my podcast, Body Stuff, and we’ll talk more about the innate and adaptive immune systems (click here to learn more and hopefully subscribe). Some toll-like receptors are very sensitive to mRNA, which makes sense as these receptors are trying to protect us from bacteria and viruses, like COVID-19. Activation of toll-like receptor 3 (TLR 3) has been associated with pregnancy complications in animal studies, so it is important to prove there are no issues with the immune system activation caused by the COVID-19 vaccine. 

Wait what? I know what you are thinking. There is a potential mechanism by which the vaccine could affect the placenta—stimulation of toll-like receptors—and people are getting the vaccine during pregnancy? 

Big breath. 

Before a vaccine goes to market, even though the initial human studies don’t include pregnant people, there are animal studies that evaluate the potential impact on pregnancy. These are called developmental and reproductive toxicity (DART) studies, and they involve giving the vaccine to pregnant animals that are good models for the human response. There has been no suggestion of any concern with the Pfizer-BioNtech, Moderna, Johnson & Johnson/Janssen, or Oxford-AstraZeneca COVID-19 vaccines. If there were an issue with toll-like receptors, the vaccine, and pregnancy we would see it here. Meaning, we’d already know. As an aside, these DART studies cannot inform us about the effects of vaccines on menstruation as they are typically done on rats or mice and they don’t menstruate, they have an estrus cycle, which is totally different. In addition, the CDC has been tracking outcomes of those who were vaccinated during pregnancy or shortly thereafter and there has been no increased risk of pregnancy complications.

This new study simply adds the safety data for pregnancy and, according to an interview with one of the study authors, hopefully more information to reduce vaccine hesitancy. The researchers evaluated the placentas of 84 women who received the vaccine and 116 who did not, to look for microscopic changes that could signify a concerning impact on the placenta. They found nothing alarming. To put this in perspective, two other studies have looked at the effect of COVID-19 infection on the placenta, and both showed that placentas from women infected with COVID-19 were significantly more likely to have concerning changes related to blood clotting, in one of the studies 50% of placentas were affected

We have an ever growing body of literature showing there is no concern related to COVID-19 vaccination during pregnancy, and this latest study shows us that unlike infection with COVID-19, the vaccine appears to have no negative effect on the placenta. 

To review

  • Animal studies (DART studies) show no safety concerns in pregnancy.

  • Human observational studies have shown no negative consequences of vaccination with COVID-19 vaccination during pregnancy. 

  • COVID-19 infection during pregnancy is associated with a significant increased risk of death for the pregnant individual and serious pregnancy complications.

  • Infection with COVID-19 can cause concerning changes to the placenta.

  • The placentas of people who are vaccinated during pregnancy do not show any concerning changes.

There will be more studies, but there has yet to be even a single study showing a concern with COVID-19 vaccine during pregnancy, and that must be weighed against the many studies showing serious harm from infection with COVID-19 during pregnancy. 

The only logical conclusion can be that people who are spreading lies about the vaccine and pregnancy, such as Northrup and Wolf, are actively trying to increase increase the rate of death for pregnant individuals, as well as increase the rate of premature delivery and stillbirth. Or, the fact that people will die, and lives irrevocably harmed by increasing vaccine hesitancy, is an unimportant consequence in their quest for infamy.