Pfizer’s mRNA COVID Shot Can Cause Unintended Immune Responses

A new study by published in the journal Nature last week revealed that the mRNA (messenger ribonucleic acid) COVID-19 gene therapies can unexpectedly cause cells of the body to misread the mRNA coding and produce unintended proteins (also known as ribosomes), a process described in the study as “frameshifting.”^{1 2 3 4 5}

The study by the Medical Research Council (MRC) Toxicology Unit at Cambridge University in England found that “bases with a chemical modification called N1-methylpseudouridine, which are currently contained in mRNA therapies,” are behind these misreads or “slips” along the mRNA sequence.³

One-Third of Vaccinated Individuals Experienced “Off-Target” Immune Responses

The study, which involved lab work on Pfizer/BioNTech’s Comirnaty shot in mice and subsequently on 21 people, found that about one-third of the vaccinated individuals experienced unintended immune responses. Researchers reportedly “identified the sequence within the mRNA that causes this to occur and found a way to prevent ‘off-target’ immune responses.”^{1 3}

The study shows that the use of modified nucleotides (the building blocks of RNA) to produce the mRNA COVID shots can cause the “cellular machinery that reads the recipe for the mRNA to make proteins to slow down, pause, and then start reading again, but beginning from a slightly different point in the recipe,” according to Stephen Griffin, PhD, professor of cancer virology at Cambridge University. This means that, in addition to the “main vaccine-driven immune response against the spike protein, other minor responses can also arise targeting the new protein sequences.”⁴

“The messenger RNA vaccines contain short strands of genetic code that provide the instructions for the cells in our bodies to make copies of the spike protein on the surface of the coronavirus that causes COVID-19, said Neil Mabbott, PhD, who heads the immunology division of The Roslin Institute and Royal School of Veterinary Sciences at the University of Edinburgh in Scotland. “These proteins are then used to train our immune systems to recognize and destroy the virus should we become infected with it.”⁴

Dr. Mabbott described the ability of mRNA shots to sometimes trigger a “process known as frameshift,” which can cause cells to misread the gene therapy’s mRNA, which can then create abnormal versions of the coronavirus spike protein being made.⁴

Scientists Maintain mRNA Misreads Do Not Make COVID Shots Harmful

But Dr. Mabbott suggested that the ribosome misreads identified in the study should be of no concern in terms of the safety or effectiveness of mRNA COVID shots. He said:

The findings in this study do not suggest that these frameshift mistakes are harmful to the body, nor do they suggest they are associated with the very rare adverse reactions to the vaccines that some people have experience such as myocarditis. By showing how these frameshift mistakes can prevented this provides an excellent opportunity to increase the efficacy of the mRNA vaccines and further improve their safety profile.⁴

Sheena Cruickshank, PhD, immunologist and professor in biomedical sciences and public engagement at the University of Manchester in England, agreed. Although she maintained that, currently, there is no evidence that the mechanism described in the study is behind any of the adverse reactions linked to either of the two mRNA COVID shots—Comirnaty or Moderna’s Spikevax—it is “unclear” whether the safety or efficacy profile of the shots is being affected:

[I]t is unclear that this potential mechanism is having any impact in the current vaccination efficacy or safety.³

Dr. Griffin accepts that some people who have received the mRNA COVID shots have suffered “rare side effects that are more serious because humans are so genetically diverse,” but maintained that the study does not link the mRNA misreads to these side effects. However, he cautioned that this view will, “naturally, have to be confirmed beyond any doubt going forward.”⁴

Rolf Marschalek, PhD, a molecular biologist at Goethe University Frankfurt in Germany, said he would like to see more evidence about whether or not the mRNA misreads are a “significant issue” for modified mRNA therapies.⁵

If you would like to receive an e-mail notice of the most recent articles published in The Vaccine Reaction each week, click here.