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Vaccines can contain trace amounts of materials left over from their manufacturing process. One of these materials is DNA, which can remain in both mRNA vaccines and a variety of older vaccines. This DNA is expected and considered safe, and there are purification and quality control steps meant to ensure it is present within regulatory limits.

We have covered unsubstantiated claims that residual DNA in mRNA COVID-19 vaccines is considered “adulteration” or integrates into people’s DNA and causes cancer. Representatives from regulatory agencies and various academic experts told us there isn’t reason to believe the small amounts of residual DNA in the mRNA vaccines would integrate into a person’s cellular DNA and cause cancer. And legal experts told us that the residual DNA would not be considered adulteration.

(For more about residual DNA in mRNA vaccines, read our article “COVID-19 Vaccines Have Not Been Shown to Alter DNA, Cause Cancer.”)

In a twist on these claims, recent social media posts shared a headline falsely stating that “Moderna Admits mRNA Jabs Cause Turbo-Cancer” and referencing the residual DNA found in vaccine vials. The headline is from an article published by the People’s Voice, a website with a history of spreading misinformation and publishing false headlines.

As we also have written previously, there isn’t reason to believe the mRNA vaccines cause very aggressive cancer, or “turbo cancer.”

The new false claim, that Moderna has admitted the mRNA vaccines cause turbo cancer, stems from misleading statements made by Dr. Robert Malone, who has spread COVID-19 misinformation in the past. Malone made his remarks during a Nov. 13 event held and livestreamed by Rep. Marjorie Taylor Greene.

Malone referred to a short section in a Moderna patent application, published in 2019. The patent application is related to RNA vaccines, but the comments Malone highlighted are about DNA vaccines, which remain experimental in the U.S.

In its description of DNA vaccines, the Moderna patent application mentioned some theoretical cancer-related concerns as an example of a drawback of the technology: “With this technique, however, comes potential problems, including the possibility of insertional mutagenesis, which could lead to the activation of oncogenes or the inhibition of tumor suppressor genes.”

Insertional mutagenesis is a phenomenon in which foreign DNA integrates into a genome, causing changes. The concern the patent application references is that the DNA could integrate in precisely the wrong place in a cell’s DNA and turn on a gene that could contribute to cancer or turn off a gene that helps protect cells from becoming cancerous.

“FDA says they’re not aware of any concerns, but Moderna in its own patent lays out exactly the same concerns that exist about DNA and insertional mutagenesis and genotoxicity,” Malone said.

But the concerns mentioned in the patent application were about vaccines using DNA as their main ingredient, not residual DNA left over in other types of vaccines. DNA vaccines rely on getting DNA into the nucleus of a cell, where it is transcribed into mRNA, which is used to make protein. The messenger RNA, or mRNA, vaccines work by introducing mRNA into the body of a cell, where it serves as instructions for making protein.

With residual DNA, scientists from the U.S. Food and Drug Administration have written that they consider the primary cancer-related concern to be the introduction of DNA encoding an activated cancer-causing gene. There is no residual DNA encoding cancer-causing genes in the mRNA COVID-19 vaccines.

The patent application also makes clear that even for DNA vaccines, the concern is theoretical. What the line quoted from the patent application does not spell out is that this “potential” concern has not been demonstrated to be a real safety problem, even for DNA vaccines.

In a 2020 review paper on mRNA vaccines, FDA scientists nodded to the theoretical concerns about insertional mutagenesis from DNA vaccines, while making clear they did not consider this risk to have been borne out.

In listing advantages of mRNA vaccines over DNA vaccines, they referred to the absence of the “perceived” risk of DNA integrating into a person’s own DNA. They went on to explain that this was a concern with DNA vaccines in the past, but experiments have shown that the rate of integration was low, “thus lessening the concern for integration.”

In a response sent to us for our prior article on residual DNA in the mRNA COVID-19 vaccines, an FDA spokesperson did in fact make reference to past concerns about DNA integration and cancer, while expressing confidence in the mRNA vaccines.

The FDA email said that “with regard to the mRNA vaccines, while concerns have been raised previously as theoretical issues, available scientific evidence supports the conclusion that the minute amounts of residual DNA do not cause cancer or changes to a person’s genetic code.”