Claim that COVID-19 mRNA vaccines contain DNA contaminants based on study of vials of “unknown provenance”; no evidence COVID-19 mRNA vaccines can alter DNA in people
To date, claims that COVID-19 mRNA vaccines can alter DNA in people lack a biologically plausible mechanism to explain how this would happen. A certain proportion of polio vaccine administered between the 1950s and 1960s were contaminated with the virus SV40, which can cause tumors in animals. However, epidemiological studies since then haven’t detected a higher risk of cancer in people who received the polio vaccine at that time period.
Misleading: While SV40 is known to cause cancer in certain animals like hamsters, epidemiological studies didn’t find an elevated risk of cancer in people who received SV40-contaminated polio vaccine.
Inadequate support: Neither the preprint by McKernan et al. nor the other studies cited in the article provided evidence for the claim that COVID-19 mRNA vaccines contained significant DNA contamination or that the vaccines can alter DNA in people. The analysis underpinning this claim was performed on vials of unknown origin.
On 11 June 2023, The Epoch Times republished an article by osteopath Joseph Mercola, which carried the headline “Monkey Virus DNA Found In COVID-19 Shots”. The article claims that a group of scientists had found “massive DNA contamination in the mRNA COVID-19 shots, including simian virus 40 (SV40) promoters”; that “SV40 has been linked to cancer in humans”; and that “The finding of DNA means the mRNA COVID shots may have the ability to alter the human genome”.
The same article was also republished by the website Discern Report. Both articles together accrued more than 10,000 engagements on social media to date, according to the social media analytics tool CrowdTangle. However, the article’s content is misleading and the claims are unsubstantiated by evidence, as we will explain below.
Preprint finding of DNA contamination in COVID-19 vaccine used vials of unknown origin
The article’s claims draw heavily on a preprint (a study not yet peer-reviewed) authored by McKernan et al., a group of scientists at Medicinal Genomics, a company that offers nucleic acid sequencing services.
In the preprint, the authors claimed that they detected DNA in the Pfizer-BioNTech COVID-19 vaccine and in particular a particular gene sequence originating from the simian virus 40 (SV40). The gene sequence is known as a promoter, which can enhance expression of a gene that is located after the promoter. The U.S. National Human Genome Research Institute explains more about the role of promoters in this article. It is this finding that forms the basis for the article’s claim that COVID-19 mRNA vaccines could modify DNA and increase cancer risk.
However, one of the most significant limitations is that the vials tested were of “unknown provenance” and the authors explained that the vials had been sent to them “anonymously in the mail without cold packs” but that the vials were “unopened”. Simply put, whether the vials were actually of COVID-19 mRNA vaccines and the integrity of the contents is questionable. The Epoch Times article simply glossed over this fact, discussing the preprint findings as conclusive evidence of DNA contamination when this is far from certain.
Michael Imperiale, a professor at the University of Michigan who studies DNA tumor viruses, told Health Feedback in an email that the results are far from establishing that DNA contamination of COVID-19 mRNA vaccines is widespread. “Since this article has not been peer reviewed, we don’t know if there was truly significant DNA contamination,” he explained. [Read Imperiale’s feedback in full here.]
The Epoch Times also asserted that “Regulatory Agencies Knew There Was a Contamination Problem”, based on a Substack article by the preprint’s first author, and that “Data submitted to the EMA by Pfizer shows sampled lots had anywhere from 1 ng/mg to 815 ng/mg of DNA”.
It’s important to note that the upper limit of 815 ng DNA/mL RNA came from a lot that had been treated with the incorrect DNase stock, as the footnote on the report clearly showed, resulting in more residual DNA left in the vaccine. This fact however, is glossed over by The Epoch Times.
Were we to exclude that value, the highest value would be 211 ng DNA/mL RNA, which is within the “commercial acceptance criterion” of the European Medicines Agency (≤330 ng DNA/mg RNA) stated in the report.
Furthermore, vaccine vials with significant residual DNA levels exceeding that criterion wouldn’t be used for vaccination in the first place. This would also be the case in the U.S., Imperiale pointed out.
Others also pointed out that since quantifying residual DNA levels is based on a measurement relative to RNA levels, vials that weren’t stored properly are likely to experience significant RNA degradation. In contrast, DNA would be more stable and less likely to degrade. This could produce spurious results as DNA levels could thus be much higher than RNA levels by the time the analysis was conducted.
No evidence to date that SV40 causes cancer in humans
The claim that SV40 is associated with cancer harkens back to early reports of SV40 contamination in polio vaccines that were used between the 1950s and 1960s. SV40 is a DNA virus that is found in both monkeys and humans, and has been reported to cause cancer in some animals, such as hamsters[2,3].
The U.S. Centers for Disease Control and Prevention (CDC) explains:
“From 1955 to 1963, an estimated 10-30% of polio vaccines administered in the US were contaminated with simian virus 40 (SV40). The virus came from monkey kidney cell cultures used to make polio vaccines at that time. Most of the contamination was in the inactivated polio vaccine (IPV), but it was also found in oral polio vaccine (OPV). After the contamination was discovered, the U.S. government established testing requirements to verify that all new lots of polio vaccines were free of SV40.”
The news of the contamination therefore led to concerns that people who’d received the polio vaccine during that time period could be at a higher risk of cancer.
Several epidemiological studies have since been performed on populations that received the polio vaccine during that time period. These didn’t find a heightened risk of cancer in these people[4-7], which is inconsistent with the claim that SV40 increases cancer risk. Health Feedback covered this subject in an earlier review. The Children’s Hospital of Philadelphia also addresses this subject in this article.
In 2002, the U.S. Institute of Medicine published a review on the relationship between SV40 and cancer. In its Executive Summary, it concluded:
“Although SV40 has biological properties consistent with a cancer-causing virus, it has not been conclusively established whether it might have caused cancer in humans. Studies of groups of people who received polio vaccine during 1955–1963 provide evidence of no increased cancer risk. However, because these epidemiologic studies are sufficiently flawed, the Institute of Medicine’s Immunization Safety Review Committee concluded that the evidence was inadequate to conclude whether or not the contaminated polio vaccine caused cancer.”
There are a few things to keep in mind here. Firstly, the preprint claimed to have found only a fragment of the SV40 genome (the promoter), not the full virus. The preprint’s lead author told AP News that “that’s not the same as finding the full SV40 virus in the shot”. And it is the virus that has been associated with cancer in animals, not the promoter fragment alone.
Secondly, the polio vaccine contamination with SV40 was the result of using monkey kidney cells to grow the polio virus used to manufacture the vaccine. The making of the Pfizer-BioNTech COVID-19 mRNA vaccine on the other hand, doesn’t involve such cell cultures, raising questions about the origin of the alleged SV40 contamination detected by the scientists.
No plausible mechanism for COVID-19 mRNA vaccines to alter DNA
The Epoch Times article cited the preprint’s first author Kevin McKernan, formerly the R&D lead for the MIT Human Genome Project and currently chief scientific officer at Medicinal Genomics, who stated that “the concern that people, even at the FDA, have noted in the past whenever injecting double-stranded DNA, is that these things can integrate into the genome”. The Epoch Times article also claimed that “the finding of DNA means the mRNA COVID-19 vaccine may alter the human genome”.
The claim that COVID-19 mRNA vaccines can alter our DNA is an enduring one that can be traced all the way back to 2020, when the vaccines were under development. Scientists interviewed by Health Feedback explained that there’s no known biological mechanism that allows COVID-19 mRNA vaccines to alter DNA; their comments were included in these two reviews.
The Epoch Times article however offered a new twist to this claim, proposing that it is DNA contaminants in the vaccine, particularly the SV40 promoter, rather than the spike mRNA, that can modify our DNA.
But “there is no evidence that the SV40 promoter can act as a so-called insertional mutagen, i.e., integrate next to a cellular oncogene and activate its expression,” Imperiale told Health Feedback.
The Epoch Times article cited microbiologist Sucharit Bhakdi, who claimed that “cytoplasmic transfection”, during which the membrane surrounding the nucleus of the cell (where DNA is housed) is dissembled during cell division (mitosis), can “allow for genetic manipulation”.
However, Imperiale pointed out that “since the vaccine is delivered into muscle, which contains mostly post-mitotic cells, the idea of cytoplasmic-nuclear mixing does not apply”. Post-mitotic cells –common examples include nerve cells and skeletal muscle cells– are generally understood to no longer undergo mitosis.
Preprint author’s reaction to our request for comment
We reached out to McKernan to ask for clarification regarding his claim that SV40 promoters could integrate into the human genome. McKernan didn’t respond to our email, but posted our email on Twitter.
In his Twitter thread, McKernan alleged Health Feedback is “obsessed with reducing population levels”; incorrectly claimed that we’d asserted only retroviruses can integrate into the human genome; and cited a PNAS article as evidence to support his claim, stating that “If non-retrovirus mRNA can integrate, DNA is even easier”.
The PNAS article in question, authored by Zhang et al., detected parts of the SARS-CoV-2 genome integrated into the genome of an immortalized human cell line (cells that can proliferate indefinitely like HeLa cells), following infection by SARS-CoV-2.
The authors reported that this integration was facilitated through the LINE-1 retrotransposon system, which is present in the human genome. Health Feedback discussed the LINE-1 retrotransposon system in greater detail in this review regarding a claim based on a study by Alden et al.
One caveat is that the PNAS study used genetically modified human cells that overexpress LINE-1, whereas normal human cells don’t, which raises questions about how likely the effect observed in the study would occur in people.
The PNAS article generated controversy in the scientific community, as other scientists reported being unable to replicate the results, raising questions about the generalizability and reliability of the findings.
McKernan also cited a 1999 study by Dean et al., which reported that including certain parts of the SV40 promoter on a plasmid (a circular extrachromosomal DNA molecule) improved the movement of the plasmid into the nuclei of monkey kidney cells growing in cell culture and led to improved gene expression of genes on the plasmid. However, it didn’t show the plasmid integrating into the genome of the cells. The study offers no evidence that integration in the context of vaccination occurs.
In brief, McKernan’s Twitter thread contained no answers regarding our questions. Instead, he asked Twitter users to “address [our] questions”.
It is worth noting that in February 2023, Zhang et al. (the authors of the PNAS article cited by McKernan) published a study in the journal Viruses, which followed up on their earlier findings regarding LINE1-mediated SARS-CoV-2 integration into human DNA. They examined both SARS-CoV-2-infected cells and mRNA-transfected cells for signs that SARS-CoV-2 mRNA had integrated into the cells’ DNA. The mRNA-transfected cells serve as a model for what happens in mRNA vaccination, albeit imperfectly.
They found that while virus-infected cells showed signs of SARS-CoV-2 integration into the human genome, cells transfected with mRNA from the virus didn’t.
The authors concluded that “Retrotransposition in virus-infected cells, in contrast to transfected cells, may be facilitated because virus infection, in contrast to viral RNA transfection, results in significantly higher viral RNA levels and stimulates LINE1 expression by causing cellular stress.”
A press release by the Whitehead Institute also pointed out the same finding:
“The researchers found that transfection of SARS-CoV-2 mRNA did not lead to genomic integration in the same way that infection did. Infection naturally produces a large amount of viral RNA and causes an inflammatory response in cells. Such cellular stresses increase the level of the reverse transcription machinery. Transfection does not do this, and correspondingly, the researchers found no evidence with TagMap that it led to viral genomic integration by LINE1 in normal cells.”
Rudolf Jaenisch, a senior author of both the PNAS and Viruses studies and a co-founder of the Whitehead Institute, stated that “our results are consistent with vaccine RNA not integrating”, although he cautioned that further research using the actual mRNA vaccine was still needed.
McKernan didn’t mention this study in his Twitter thread reacting to our email.
In summary, the Epoch Times article’s proposal that DNA contaminants in COVID-19 mRNA vaccines pose a risk of DNA modification and cancer isn’t substantiated by sufficient evidence. While a preprint claimed DNA contaminants were present in an alleged vial of Pfizer COVID-19 mRNA vaccine, this finding came from a vial of unknown origin. Yet this fact is glossed over and the preprint finding is discussed as conclusive evidence of contamination despite this significant limitation.
The preprint also offered no evidence that COVID-19 mRNA vaccines cause DNA alterations nor a plausible mechanism for this to occur, and the Epoch Times article’s claim that SV40 is associated with cancer is misleading, as studies so far haven’t shown that this association is a causal one.
Professor, Department of Microbiology and Immunology, University of Michigan
Let me preface my answer with the caveat that since this preprint has not been peer reviewed, we don’t know if there was truly significant DNA contamination. I am certain that the FDA does not allow the release of lots of vaccine that have such contamination.
There is no evidence that the SV40 promoter can act as a so-called insertional mutagen, i.e., integrate next to a cellular oncogene and activate its expression. Moreover, since the vaccine is delivered into muscle, which contains mostly post-mitotic cells, the idea of cytoplasmic-nuclear mixing does not apply. Next, even if the DNA entered the nucleus, integration of any plasmid into the cell genome would be an extremely rare event. And finally, since these cells are expressing a viral antigen (the SARS-CoV-2 Spike protein), they will be destroyed by the immune system.
- 1 – McKernan et al. (2023) Sequencing of bivalent Moderna and Pfizer mRNA vaccines reveals nanogram to microgram quantities of expression vector dsDNA per dose. OSF. [Note: This is a preprint that has yet to be peer-reviewed at the time of this review’s publication.]
- 2 – Girardi et al. (1962) Development of Tumors in Hamsters Inoculated in the Neonatal Period with Vacuolating Virus, SV40. Experimental Biology and Medicine.
- 3 – Cicala et al. (1993) SV40 induces mesotheliomas in hamsters. American Journal of Pathology.
- 4 – Pankhurst et al. (2001) Thirty-five year mortality following receipt of SV40-contaminated polio vaccine during the neonatal period. British Journal of Cancer.
- 5 – Engels et al. (2003) Cancer Incidence in Denmark Following Exposure to Poliovirus Vaccine Contaminated With Simian Virus 40. Journal of the National Cancer Institute.
- 6 – Engels et al. (2003) Childhood exposure to simian virus 40-contaminated poliovirus vaccine and risk of AIDS-associated non-Hodgkin’s lymphoma. International Journal of Cancer.
- 7 – Rollison et al. (2004) Case-Control Study of Cancer among US Army Veterans Exposed to Simian Virus 40-contaminated Adenovirus Vaccine. American Journal of Epidemiology.
- 9 – Zhang et al. (2021) Reverse-transcribed SARS-CoV-2 RNA can integrate into the genome of cultured human cells and can be expressed in patient-derived tissues. PNAS.
- 10 – Parry et al. (2021) No evidence of SARS-CoV-2 reverse transcription and integration as the origin of chimeric transcripts in patient tissues. PNAS.
- 11 – Zhang et al. (2023) LINE1-Mediated Reverse Transcription and Genomic Integration of SARS-CoV-2 mRNA Detected in Virus-Infected but Not in Viral mRNA-Transfected Cells. Viruses.