Fact check: A false post on social media claims COVID-19 vaccine causes infertility in women

The claim: The COVID-19 vaccine can cause infertility in women

An image going viral on Facebook and elsewhere on social media is lodging a concerning complaint: The COVID-19 vaccine could lead to infertility in women. This comes as the first doses of the Pfizer-BioNTech vaccine are delivered and administered across the USA

The image, a screenshot of what appears to be a news article, declares the vaccine is "female sterilization," according to an unidentified Pfizer head of research. How exactly this is accomplished is through a protein contained in the vaccine, one integral for placenta formation.

"The vaccine contains a spike protein (see image) called syncytin-1, vital for the formation of the human placenta in women," the article's nameless author writes. 

"If the vaccine works so that we form an immune response AGAINST the spike protein, we are also training the female body to attack syncytin-1, which could lead to infertility for an unspecified duration."

Similar images on Facebook attribute the fertility concern to Drs. Wolfgang Wodarg and Mike Yeadon. Wodarg, a German physician, and Yeadon, a former Pfizer chief science officer and research head, jointly filed a petition with the European Medicines Agency on Dec. 1 calling for suspension of Pfizer-BioNTech and other biotech/pharmaceutical companies' COVID-19 vaccine efforts.   

Yeadon has been criticized for making misleading and inaccurate claims about the virus; he has not worked at Pfizer since 2011, according to his LinkedIn profile. Wodarg himself has been controversial, calling the 2009-2010 H1N1 swine flu pandemic "fake" and contributing to a COVID-19 misinformation video.    

USA TODAY has reached out to the Facebook users who shared the images.    

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What is syncytin-1? 

In February 2000, researchers at the now-defunct Genetics Institute in Cambridge, Massachusetts, discovered a gene, residing within the human genome, containing hallmarks of a recently discovered human endogenous defective retrovirus.

The protein encoded by the viral gene was produced only by cells of the placenta – an organ made only during pregnancy that exchanges oxygen and nutrients from mother to fetus – that come into direct contact with the uterus. A sturdy bond between maternal uterine and fetal placental cells was entirely dependent on this protein, which the researchers called syncytin from the word syncytium, a cell-like structure formed from the joining of many other cells.

Later research discovered that humans were not the only ones carrying this anchoring protein: Chimpanzees, gorillas, orangutans and gibbons possessed the same gene along the same spot in their genomes, hinting at inheritance from a common hominid ancestor. Syncytin was also found in other mammals, although the gene did not appear to originate from the same virus. 

A second syncytin was identified by French virologist Dr. Thierry Heidmann and colleagues in 2003. Both syncytins – dubbed syncytin-1 and 2 – were important for placenta formation, but syncytin-2 played an additional role in preventing the mother's immune system from attacking the fetus, a typical reaction of any healthy immune system when confronted with a foreign presence.     

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Not the same proteins

Pfizer-BioNTech and Moderna's COVID-19 vaccines both use messenger RNA, a single-strand of genetic code that provides manufacturing instructions for a particular protein, much like a recipe. For the vaccine, the recipe is for SARS-CoV-2's spike protein, which cells will mass produce, triggering and teaching the body to make antibodies in response.

The mRNA degenerates once its purpose is fulfilled, but the anti-SAR-CoV-2 spike protein antibodies live on to fight future infection.  

While the coronavirus spike protein and syncytin-1 do share a minute string of amino acids – the building blocks of proteins – the similarity is too small to warrant an immunologic offensive, said virologist Dr. Ian Jones of the University of Reading, United Kingdom, to FullFact.org.     

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Duke University immunologist Dr. Stephanie Langel also agreed, saying in an interview with the New York Times that the two proteins have "almost nothing in common, making the vaccine highly unlikely to trigger a reaction."

Additionally, Pfizer spokeswoman Jerica Pitts confirmed the vaccine did not affect female fertility.

"It has been incorrectly suggested that COVID-19 vaccines will cause infertility because of a shared amino acid sequence in the spike protein of SARS-CoV-2 and a placental protein," she said in an email to the Associated Press.

"The sequence, however, is too short to plausibly give rise to autoimmunity."

It is also worth noting that since late January, there have been over 44,000 COVID-19 cases among pregnant women, according to the Centers for Disease Control and Prevention. If anti-SAR-CoV-2 spike protein antibodies produced by the mother were attacking syncytin-1, and thereby the placenta, pregnancy complications or miscarriages would prevail, said Dr. Mary Jane Minkin, clinical professor of obstetrics and gynecology at Yale School of Medicine, to USA TODAY. So far, there has been no evidence of the kind reported among pregnant women. 

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Our ruling: False

We rate the claim that the COVID-19 vaccine causes female infertility as FALSE because it is not supported by our research. The claim originates from a petition filed by Drs. Wolfgang Wodarg and Mike Yeadon, the latter an ex-employee of Pfizer who last worked with the company in 2011. The protein mentioned in the claim, syncytin-1, is important for placenta formation, but it bears no resemblance to the SARS-CoV-2 spike protein save a very small amino acid sequence. Experts agree this similarity is not enough to trigger an immune response leading to female infertility.

While the vaccine has not been tested in pregnant women, there are over 44,000 COVID-19 cases among pregnant women in the USA. Any indication of an adverse immune reaction related to syncytin-1 would manifest in pregnancy complications or miscarriages; thus far, none has been reported.

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