COVID-19 Vaccine-Generated Spike Protein is Safe, Contrary to Viral Claims

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Hundreds of millions of COVID-19 vaccine doses have been administered safely in the United States in the last six months. There is no evidence to indicate that the spike proteins generated by human cells following vaccination are a toxin or that they circulate in the body and damage tissues, contrary to what a Canadian virus immunologist recently claimed. 

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All of the COVID-19 vaccines currently approved in the United States are designed to instruct human cells to make harmless spike proteins — mimicking a viral protein that’s used by the SARS-CoV-2 virus to enter cells. When the immune system recognizes the proteins, which aren’t normally there, it starts generating antibodies and building an immune response against it. The process prepares the body against future infection. 

These vaccines have been found to be effective and safe in clinical trials with tens of thousands of participants, and in real world conditions with over 325 million doses administered.

According to the Centers for Disease Control and Prevention, the “most intensive safety monitoring in U.S. history” has found that most of the reported side effects after COVID-19 vaccination are minor, such as pain at the injection site or fever. Severe adverse reactions to the vaccines have been rare

Yet, a Canadian virus immunologist recently claimed that the vaccine’s spike protein is “a pathogenic protein,” “a toxin” that gets into the bloodstream, then accumulates in breast milk and “in a number of tissues” and could lead to cardiovascular and neurological damage in adults, children and infants. 

“We made a big mistake,” said Byram Bridle, a viral immunologist and associate professor at the University of Guelph’s Ontario Veterinary College, during an interview with Canadian radio personality Alex Pierson on May 27. “We thought the spike protein was a great target antigen, we never knew the spike protein itself was a toxin and was a pathogenic protein. So by vaccinating people we are inadvertently inoculating them with a toxin.”

According to his profile, Bridle’s research focuses on biotherapies for the treatment of cancers and the way organisms respond to viruses. Since the pandemic started, his lab has been trying to develop vaccines against coronaviruses, for which he received a $230,000 grant from the Ontario government. 

Bridle’s interview was reposted by several publications, including one owned by Robert F. Kennedy Jr.’s anti-vaccination organization. Segments of the interview were widely spread in social media platforms in English and Spanish

But researchers and health officials told there is no “mistake” and that there is no evidence to support Bridle’s claims. 

There is no evidence that the spike protein in vaccines “is toxic or that it lingers at any toxic level in the body after vaccination,” an FDA spokesperson told us in an email.

Jason McLellan, a structural biologist at the University of Texas at Austin who has been studying spike proteins in other coronaviruses for years and whose work was fundamental for the development of COVID-19 vaccines, said Bridle’s statements are not correct.  

“The spike protein is not pathogenic. It is not a toxin,” McLellan told us in an email. “I have not seen any data to support what Bridle claims.”

No Evidence Vaccine-Generated Spike Protein Lingers in Bloodstream

Bridle, who in the radio show said he’s “very much pro-vaccine,” says his claims are “completely backed up by peer-reviewed scientific publications in well-known and well-respected scientific journals.” 

But authors of two of the studies he cites told us their findings don’t back Bridle’s statements. 

“Bridle is taking our results and completely misinterpreting them,” said David R. Walt, a member of the faculty at Harvard Medical School and of Harvard’s Wyss Institute for Biologically Inspired Engineering, who co-authored a study that found circulating SARS-CoV-2 vaccine antigen in the plasma of vaccine recipients. 

The study, published in Clinical Infectious Diseases in May, collected plasma from 13 healthcare workers at the Brigham and Women’s Hospital in Boston who had received two doses of mRNA vaccine. Researchers detected levels of SARS-CoV-2 protein as early as one day after the first injection in 11 of the 13 participants.

Bridle presents the study as evidence that the spike protein gets into blood circulation. 

COVID-19 vaccination doses available at a Walgreens mobile bus clinic in Los Angeles. (Photo by Mario Tama/Getty Images)

Walt told us in an email that the aim of the study was to see if an ultrasensitive detection technology, a single-molecule array, could detect circulating antigen produced by the mRNA vaccine to demonstrate the vaccine is working as designed. 

“We found we could detect extremely low concentrations of S1 (a subunit of spike) in 11 of 13 healthy vaccinated individuals and the full spike in 3 of 13,” he said in an email, noting that the technology they used is 1,000 times more sensitive than a typical antigen test, “so we are really detecting minute quantities of the spike and S1 proteins.” (Emphasis is his). 

“We found that within a few days of the antigen appearing, the individuals developed antibodies that removed the antigen from the bloodstream,” he added. “Our conclusion was that the vaccine is working as intended.”  

Walt, a pathology professor, added there is no evidence that the spike protein is a pathogenic protein that causes damage in several tissues. 

“COVID, on the other hand, is known to have significant effects on many tissues and organs,” he said. “The most important message is that over 400 million doses of the mRNA vaccine have been administered with negligible serious consequences. It is incredibly safe.”

A second study Bridle uses to support his claims is one by Pfizer. In the radio interview with Pierson, Bridle says he and “other international collaborators” obtained the document through a request for information to a Japanese regulatory agency, claiming that it shows for the “first time ever” where the mRNA vaccines “go after vaccination.”

“Is it a safe assumption that it stays in the shoulder muscle? The short answer is absolutely not,” Bridle says in the radio show. “The spike protein gets into the blood, circulates through the blood in individuals over several days post vaccination, it accumulates … in a number of tissues such as the spleen, the bone marrow, the liver, the adrenal glands …  and in quite high concentrations, in the ovaries,” he said.   

Keanna Ghazvini, a Pfizer spokesperson, told us in an email that the document referred to by Bridle, which is mostly in Japanese, is a pharmacokinetics overview of the company’s vaccine. Pharmacokinetics is the study of how a drug moves through the body, including how quickly drugs are absorbed, metabolized, and excreted. The document was “part of the submission data applied by Pfizer to PMDA (Japan’s version of FDA) for its review,” and it is publicly available online, Ghazvini said.  

“The document is about the pharmacokinetics overview seen from lab studies and we can confirm it’s not about spike proteins from the vaccine resulting in dangerous toxins that linger in the body,” Ghazvini said. 

According to a statement sent to by the National Institute of Allergy and Infectious Diseases, the vaccine-generated spike protein “is not secreted into circulation in the bloodstream.” 

Virus Spike Protein vs. Vaccine-Generated Spike Protein 

The spike proteins from the virus and the ones generated by the vaccines are “essentially the same,” McLellan, the spike protein researcher at the University of Texas at Austin, told us, noting that they have the same function, structure and way of processing.

But, he said, there is “one key difference,” in that the spikes encoded by the vaccines “contain 2 amino acid changes that help stabilize the spike in its initial conformation and help prevent the spike from undergoing a conformational change that is required to facilitate membrane fusion.”

That’s because the SARS-CoV-2 spike protein is a shape-shifter. To fuse its viral membrane with the host cell membrane it substantially changes its shape from an unstable pre-fusion state to a stable post-fusion state. While previously working on a vaccine for MERS, a disease caused by another coronavirus, McLellan and others discovered that by adding two proline molecules to the spike protein, they could lock it into its pre-fusion state, triggering a more effective immune response and preventing cell entry. The same harmless mutation, called 2P, as in two proline molecules, is used in the SARS-CoV-2 vaccines. 

During a SARS-CoV-2 infection, the NIAID told us, the virus spike proteins can latch onto human cells, allowing the virus to infect them. With the live virus, the protein “attaches to receptors on the surface of cells and fuses the viral membrane with the host-cell membrane,” McLellan said.

However, vaccine-generated spike proteins can’t do that fusion because they are locked in the pre-fusion shape.

“The spike protein encoded by the mRNA vaccines (Moderna and Pfizer/BioNTech) and the J&J vaccine instruct the cells in our arm (where the injection is given) to produce spike protein that is tethered to the surface of the cell. It is not secreted and thus does not float through the body,” McLellan said. 

According to the NIAID statement, “the spike protein is only detectable for a few days after immunization” in tests conducted in animals. 

No Evidence Vaccine-Generated Spike Protein is Harmful reached out to Bridle for comment. In response we got an automatic email reply saying he “cannot respond” because “his workload has become challenging to manage” after the radio interview, which led to “vicious attacks by some.”

In two documents prepared in response to the attention brought by the interview, Bridle says the Canadian government “should be called upon to immediately halt the mass vaccination program of children and adolescents.” He says “there is no immediate threat of severe COVID-19 in the majority of Canadian children and adolescents,” and that more safety and efficacy data is needed for the “use of experimental vaccines.”

In May, Canada authorized the use of the Pfizer/BioNTech COVID-19 vaccine in children 12 to 15, following authorization of the vaccine in youth 16 years old and older in December. The Canadian Paediatric Society recommends offering the vaccine “to all children and adolescents 12 years of age and older as soon as vaccine supply permits.”

In a document published in June, Bridle says severe SARS-CoV-2 infections “can cause damage to the cardiovascular system” and “neurological problems.” 

“[T]he spike protein from SARS-CoV-2 might be responsible for at least some of the damage that occurs in severe cases of COVID-19,” he says, citing a study published in March in Circulation Research. 

The study, in which researchers administered a pseudovirus to hamsters, found the spike protein “alone can damage vascular endothelial cells.” But as the authors mention, the use of a pseudovirus is a limitation and “findings need to be confirmed with the SARS-CoV-2 virus” in the future.

Furthermore, the study concludes that vaccines not only protect people from SARS-CoV-2 infection, but also from damage to the endothelium, a thin membrane that lines the inside of the heart and blood vessels.

According to a statement sent to by NIAID, if “enough excess spike proteins are shed into the bloodstream and bind to human cells expressing the ACE2 receptor, an infected person could theoretically experience additional symptoms. However, this is theoretical; the exact mechanism by which COVID-19 infection leads to cardiovascular symptoms is still unclear.” 

Susan Weiss, a coronavirus researcher and professor of microbiology at the Perelman School of Medicine at the University of Pennsylvania, says there is “not much virus in the blood following infection with SARS2.” 

“I am quite confident that the spike protein is not a toxin,” she told in an email. “Furthermore if vaccine induced spike were pathogenic wouldn’t we see a lot of illness following vaccination?” 

Study on Vaccine Transfer into Breast Milk Distorted

Finally, Bridle says there is evidence that the mRNA vaccines get transferred through breast milk, citing a preprint from Singapore that tested milk samples from 10 lactating healthcare workers after they were immunized with the Pfizer/BioNTech vaccine. The unpublished study found antibodies in the breast milk from all of the workers and “minimal amounts of vaccine mRNA.”

“36 out of 40 (90%) samples did not show detectable levels of vaccine mRNA. The highest concentration of BNT162b2 mRNA in the tested samples was 2 ng/mL … a hypothetical 0.667% of the original vaccine dose being transferred in 100 mL of human milk,” the study says. “This miniscule amount of mRNA is expected to be readily destroyed by enzymes in the infant’s gut,” the authors say in the discussion.

The study concluded “lactating individuals should continue breastfeeding” after being vaccinated.

Bridle omits this information in his 37-page document, instead saying that detection of the mRNA “was downplayed.”   

“Now we know the spike protein gets into circulation. Any protein in the blood will get concentrated in breast milk,” he said on the radio show. “Looking into the adverse event database in the United States, we have found evidence of suckling infants experiencing bleeding disorders in the gastrointestinal tract.”

As we’ve reported, the Vaccine Adverse Event Reporting System is designed to detect potential problems — that’s why it’s there — but it does not show whether the vaccines caused any of the reported issues. Anyone can submit a report of an event to VAERS, even if it’s not clear that a vaccine caused the problem, and all of the notifications are accepted without determining if the event was caused by a vaccine. 

“It is unlikely that enough of the spike protein could accumulate in breast milk to have any impact on infants that consume it,” NIAID told us in a statement.  

Dr. Jeannie Kelly, an assistant professor of obstetrics and gynecology at the Washington University School of Medicine in St. Louis and lead author of a study on SARS-CoV-2 antibodies in breast milk following vaccination, told us there is no evidence to support Bridle’s claims.

“We did not measure spike protein levels in our study. However, there is no evidence that the spike protein is in breast milk,” Kelly said in an email. “Much like any other vaccination in a breast feeding person, even if the spike protein makes it into the milk, the protein would be degraded by the stomach acid. Even if the spike protein was absorbed into the blood stream, it has no mechanism of action to cause any issues such as bleeding disorders.”

According to the CDC’s website there is limited data available on the safety and the effects of vaccination in lactating people or breastfed babies because the clinical trials didn’t include people who were breastfeeding. However, it says, based on available data “COVID-19 vaccines are thought not to be a risk.”

In fact, recent studies show breastfeeding after vaccinations may provide babies with protection. 

Both the American College of Obstetricians and Gynecologists and the World Health Organization encourage women who are breastfeeding to take the vaccine. 

“There is no risk at all because all the vaccines that are being used presently, none of them have the live virus in it. And so there’s no risk of transmission through the breast milk. In fact, the antibodies that the mother has can go through the breast milk to the baby and may only serve maybe to protect the baby a little bit. But there’s absolutely no harm. It’s very safe,” says WHO’s Chief Scientist Dr. Soumya Swaminathan on a podcast produced by the organization.

Editor’s note: SciCheck’s COVID-19/Vaccination Project is made possible by a grant from the Robert Wood Johnson Foundation. The foundation has no control over our editorial decisions, and the views expressed in our articles do not necessarily reflect the views of the foundation. The goal of the project is to increase exposure to accurate information about COVID-19 and vaccines, while decreasing the impact of misinformation.


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