Florida Surgeon General Joseph Ladapo has been campaigning against the use of mRNA COVID-19 vaccines, arguing remaining DNA in the jabs could enter into human cells.

"I am calling for a halt to the use of mRNA COVID-19 vaccines," he said in the January 4 post on his official X account (screenshot here), which has been viewed millions of times and shared to Facebook.

"The U.S. Food and Drug Administration and the Centers for Disease Control and Prevention (CDC) have always played it fast and loose with COVID-19 vaccine safety, but their failure to test for DNA integration with the human genome - as their own guidelines dictate - when the vaccines are known to be contaminated with foreign DNA is intolerable."

Peter Marks, director of the Center for Biologics Evaluation and Research at the FDA, penned a formal response addressing Dr Ladapo's various claims.

He said the suggestion guidelines were not followed was simply untrue.

"In your letter, you raise questions, citing to the 2007 Guidance for Industry: Considerations for Plasmid DNA Vaccines for Infectious Disease Indications," he said. "This guidance was developed for DNA vaccines themselves, not for DNA as a contaminant in other vaccines, and is not applicable to the mRNA COVID-19 vaccines."

Kristine Dye, a virologist and molecular/cellular biologist at Florida’s Stetson University, backed up the FDA’s statement.

"Assessing the risk of DNA integration is not a standard part of vaccine approval, as Ladapo claimed, and I do not believe there is any improper procedure here by the FDA," Dr Dye said.

David Gorski, professor of surgery and oncology at Wayne State University and managing editor of the website Science-Based Medicine, told AAP FactCheck there was no merit to Dr Ladapo’s claims "from a scientific viewpoint".

Dr Gorski said he did not believe there was any improper procedure by the FDA. He has previously been critical of Dr Ladapo’s vaccine claims.

As explained by FactCheck.org, the guidelines refer to vaccines in which DNA is the primary ingredient. In mRNA vaccines, DNA is only present in residual amounts, left over from the manufacturing process.

The vaccines are made by using mRNA to create a spike protein that triggers an immune response.

"In order to make the mRNA that is contained in the vaccine, you must start with DNA," Dr Dye said.

During the manufacturing process, the DNA is refined.

"This process does a fantastic job of removing the DNA,” Dr Dye said, noting only trace amounts of DNA would be left and, as multiple health authorities including Australia's Department of Health have noted, the mRNA never enters the nucleus.

Dr Dye said the body also had systems to protect itself against foreign DNA, which were around us every day in the air and food, for example.

"All this DNA that you are constantly exposed to does not integrate into our DNA, so why would this trace, nonsense, residual DNA integrate, but not all the others?"

AAP FactCheck contacted the Florida Department of Health and Dr Ladapo’s office, but did not receive a reply.

As surgeon general, Dr Ladapo is the top health official for the state of Florida.

He is an appointee of Florida Governor Ron DeSantis, whose unsuccessful campaign to be the Republican's presidential nominee was criticised for misleading information on COVID vaccines.

Dr Ladapo has also been criticised for his comments on vaccines.

An FDA spokeswoman told AAP FactCheck Ladapo's claims about DNA integration are "untrue" and "deceptive".

“With over a billion doses of the mRNA vaccines administered and following very careful review of all the available scientific evidence, the FDA has not identified safety concerns related to the sequence of, or amount of, residual DNA," the representative said.

"Perpetuating references to information about residual DNA in COVID-19 vaccines without placing it within the context of the manufacturing process and the known benefits of the vaccine is misleading."

AAP FactCheck has previously debunked claims of the dangers of DNA integration in mRNA vaccines.