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The FDA's biologics chief issued a of the Florida Surgeon General's criticizing the agency's oversight of mRNA COVID vaccines, calling it "misleading" and equating its claims to disinformation.

Peter Marks, MD, PhD, director of FDA's Center for Biologics Evaluation and Research (CBER), strongly refuted claims made by Joseph Ladapo, MD, PhD, that the vaccines may be contaminated with DNA fragments.

"Perpetuating references to this information about residual DNA without placing it in the context of the manufacturing process is misleading," Marks wrote, concluding the letter by noting that the spread of false information around COVID vaccines was leading to serious harm.

"The challenge we continue to face is the ongoing proliferation of misinformation and disinformation about these vaccines which results in vaccine hesitancy that lowers vaccine uptake," he wrote. "Given the dramatic reduction in the risk of death, hospitalization, and serious illness afforded by the vaccines, lower vaccine uptake is contributing to the continued death and serious illness toll of COVID-19."

Ladapo's letter, which was addressed to FDA Commissioner Robert Califf, MD, and CDC Director Mandy Cohen, MD, MPH, specifically asked for information on an alleged discovery of "host cell DNA fragments" in the Pfizer and Moderna COVID-19 mRNA vaccines. He questioned whether the shots' lipid nanoparticles could ferry contaminant DNA into human cells, and whether "the presence of [Simian Virus] SV40 promoter/enhancer DNA may also pose a unique and heightened risk of DNA integration into host cells."

Marks roundly rejected these claims, offering a "general explanation of the manufacturing process" for the vaccine in the hope that "it will be helpful," explaining that residual DNA fragments in all biological products are in exceedingly small quantities.

He also said that no SV40 proteins are present in the vaccines, adding that "it is quite implausible that the residual small DNA fragments located in the cytosol could find their way into the nucleus through the nuclear membrane present in intact cells and then be incorporated into chromosomal DNA."

Marks also said that reproductive toxicology studies have found no evidence of residual DNA fragments getting into reproductive cells, a concern raised by Ladapo in his letter.

"We would like to make clear that based on a thorough assessment of the entire manufacturing process, FDA is confident in the quality, safety, and effectiveness of the COVID-19 vaccines," he wrote.

Ladapo initiated a similar exchange of letters with the FDA and CDC in March, when he challenged agency leadership on the safety profile of the mRNA COVID-19 vaccines. FDA Commissioner Califf and then-director of the CDC Rochelle Walensky, MD, MPH, responded with a scathing 4-page letter refuting Ladapo's claims about an alleged increase in reports from Florida to FDA's Vaccine Adverse Event Reporting System (VAERS).

Califf and Walensky said at the time that their letter was meant to "correct the associated misinterpretations and misinformation about the data."

Ladapo has repeatedly come under fire for his analysis and claims related to the COVID-19 vaccines. His office did not respond to a request for a comment on the FDA's response letter.

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