Confirmation of the presence of vaccine DNA in the Pfizer anti-COVID-19 vaccine

"Abstract

The rapid production of messenger RNA (mRNA)-based vaccines has been chosen as the most suitable strategy to fight the COVID-19 pandemic. Three studies reported the presence of DNA in significant amounts in Pfizer mRNA vaccines. We aimed to confirm the presence of this residual DNA. Vaccine plasmid DNA quantification using the Qubit fluorometer on a vaccine vial showed it was 216 ng/dose on average and approximately 24 times greater, reaching 5,160 ng/dose on average, after treatment with Triton-X-100. In addition, we obtained by next-generation sequencing the sequence of the complete plasmid DNA vaccine matrix (7,824 base pairs) with high coverage (98.3%) and sequencing depths (mean, 4,181-4,389 reads), indicating the presence of the plasmid DNA in high copy number. These results calls [sic] for an assessment of the copy number and nature of DNA in mRNA vaccines at a larger scale and in multiple batches, notably regarding the putative risk of DNA integration after delivery into cells.

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... [H]ere we found by several approaches and in different batches of the Pfizer BioNTech COVID-19 mRNA vaccine the abundant presence of DNA. In such vaccines, the maximal residual quantity of DNA not degraded during vaccine purification that are authorized by the European Medicines Agency and the Food and Drug Administration are 330 ng of DNA per mg of RNA, or 10 ng of DNA per dose. Our findings are in line with those of other (not peer reviewed) studies that reported the presence of DNA in Pfizer-BioNTech COVID 19 mRNA vaccine vials by qPCR and the obtaining of full-length vaccine plasmid by NGS. In the Speicher et al’s study, residual DNA quantities, ranging between 1,896 and 3,720 ng per dose were estimated using fluorometer based measurements with Qubit, and vaccine spike targeting qPCR obtained cycle threshold values ranging between 18.0 and 23.8 at 1:10 dilution, and 16.9±0.5 on undiluted vials contents. 

As a matter of fact, these results of huge quantities of plasmid DNA sequences per vaccine dose notably raise issues regarding a putative risk of its integration in the human genome after its entry into cells due to their packaging into cationic lipids. In DNA-based gene therapy, it was reported that a proportion of 10- 20% of cells are usually transfected and about 1-10% of the transiently transfected cells became stably transfected as a result of subsequent integration likely through crossover events during nuclear envelope membrane reformation at telophase. Although the potential risk that DNA found in mRNA-based vaccines integrate and either induce expression of an oncogene or shut down expression of a tumor suppressor are extremely low, this should deserve additional investigations."