healthHealth and Medicine

Fact Check: There's No Evidence The COVID-19 Vaccine Impacts Fertility


Tom Hale

Senior Journalist

clockDec 29 2020, 15:01 UTC
Vaccination in pregnancy

There’s currently no evidence to suggest the vaccine affects pregnancy. Image Point Fr/

Some rumors and claims are circulating on social media that the COVID-19 vaccine could cause problems with fertility, leading to fears that the vaccination could impact pregnant people or those looking to have kids in the future.

However, there’s currently no evidence to suggest the vaccine affects reproductive health in this way. Here’s what you need to know.


The claim goes as follows: the Pfizer/BioNTech mRNA COVID-19 vaccine might hamper the formation of the placenta, because it sparks an immune response against an amino acid sequence found in both the spike protein of SARS-CoV-2 and a protein used in placental development known as syncytin-1.

This might sound vaguely scientific, but it's actually an unsubstantiated claim dressed up in fancy language. While these two proteins share a few similar amino acids, they are largely unrelated, and experts believe the chances of the vaccination causing problems for syncytin-1 are very slim.

“I would never say never, but the possibility is vanishingly small,” Professor Jonathan Stoye, Virologist at the Francis Crick Institute, told Full Fact, an independent fact-checking organization in the UK.

Virology professor Ian Jones at the University of Reading added that syncytin-1 is “completely unrelated to the SARS [spike] protein,” leaving him to conclude the risk of infertility is “therefore essentially fictitious.”


Digging a little bit deeper into the claims on social media, it appears some of the fear stemmed from UK government advice that says pregnant people should not receive the Pfizer/BioNTech mRNA COVID-19 vaccine. It also states "if you are planning to get pregnant in the next 3 months, you should delay your vaccination." Understandably, this has led some to ask why this is the case. After all, many vaccines can be given safely before or during pregnancy, so why not this one?

The reason behind this advice is nothing sinister, it's a lack of data at this present time. The Pfizer-BioNTech vaccine is a new type of mRNA vaccine that has been proven to be effective and safe in clinical trials, but the research did not actively look to see how the vaccine affected either pregnant or lactating individuals. That said, the data so far suggest there is no cause for worry. According to a report by the US Food and Drug Administration (FDA), 23 women became pregnant while participating in Pfizer's mRNA vaccine clinical trial. Out of the 12 pregnant individuals who received the vaccine, there were no reported adverse events such as miscarriages. In the 11 who received a placebo, 2 cases of adverse effects were reported.

The evidence so far has indicated no concerns for fertility or safety in pregnancy, but public health authorities in the UK say they “want to see more non-clinical data before finalizing the advice.”

“It is standard practice when waiting for such data on any medicine,” they added. 


The US Central Disease Control And Prevention (CDC) has also published some advice for pregnant people considering the vaccination, albeit opting for a slightly more relaxed approach. They essentially argue the same points as the UK health authorities, but conclude “getting vaccinated is a personal choice for people who are pregnant.” Once again, however, they are looking for further clinical trials and additional studies to assess the safety of COVID-19 vaccines, including mRNA vaccines, administered during pregnancy.

"Based on how mRNA vaccines work, experts believe they are unlikely to pose a specific risk for people who are pregnant. However, the actual risks of mRNA vaccines to the pregnant person and her fetus are unknown because these vaccines have not been studied in pregnant women," the CDC concludes. 

For more information about COVID-19, check out the IFLScience COVID-19 hub where you can follow the current state of the pandemic, the progress of vaccine development, and further insights into the disease.

healthHealth and Medicine