CLAIM: A Swedish study shows that Pfizer’s COVID-19 vaccine changes recipients’ DNA.
THE FACTS: The study, conducted by researchers at Lund University in Sweden, tested whether the vaccine’s mRNA could be converted to DNA, and found that this was the case in certain lab-altered liver cell lines under experimental conditions. It did not assess whether the vaccine alters the human genome, or what the effects of that would be. But social media users are citing the February study to push the unproven theory that mRNA COVID-19 vaccines permanently alter recipients’ DNA.
A clip from March that is being reshared online in recent days shows three doctors, who have spread misinformation about the vaccines in the past, discussing the Swedish study and falsely claiming it demonstrates that “the Pfizer vaccine reverse transcribes and installs DNA into the human genome.” The genome is the set of instructions to build and sustain a human being. Other social media users commented that the paper proves mRNA COVID-19 vaccines “change the recipient’s DNA.”
Experts say such interpretations mischaracterize the work and draw inaccurate conclusions. The study authors clarified their research in a Q&A, stating that “this study does not investigate whether the Pfizer vaccine alters our genome,” adding that “there is no reason for anyone to change their decision to take the vaccine based on this study.”
DNA is the building block of the body’s genetic code. RNA is closely related to DNA, and one type, called messenger RNA, sends instructions to the cell. The mRNA in the COVID-19 vaccines helps train the body to recognize a protein from the coronavirus to trigger an immune response. During the study, which was conducted in a petri dish, the researchers were able to detect DNA that had been converted from the vaccine’s mRNA in a lab-modified cell that was derived from liver cancer tissue. Some viruses, like HIV, are known to be able to convert RNA to DNA and then incorporate that DNA into host cells’ genome.
Coronaviruses, however, are not expected to do this, said Bethany Moore, chair of the University of Michigan’s microbiology and immunology department. Still, the Swedish study only demonstrated that RNA had converted to DNA under the conditions created in the lab.
“Where that paper was getting a lot of press was the idea that those pieces of DNA were then getting incorporated into the genome, and there’s absolutely no evidence that that happened,” Moore said. She also cautioned that the cells used in the study were “quite different” than most cells in the body.
“In order to create these cell lines, the genetic make-up of the cells has to be ‘fiddled with’ to make them immortal and keep them alive in the petri dish,” Dr. David Strain, a senior clinical lecturer at England’s University of Exeter Medical School, wrote in an email. “These cells have had the normal protections of the immune system removed.”
Unlike the “abnormal” cells used in the study, the human body’s protections help stop imported genetic material from being “corrupted,” Strain said. Because the study design doesn’t reflect what happens in most bodies, the experts said the findings cannot be extrapolated to make inferences about human subjects. The study authors similarly pointed out in their Q&A that a limitation is that they “don’t know if what we observed in this cell line could also happen in cells of other tissue types.”
— Associated Press writer Sophia Tulp in New York contributed this report.