New Analysis Challenges Methods Used to Measure Residual DNA in mRNA Vaccines

BUFFALO, NY – August 25, 2026 – A new precision oncology paper was #published in Volume 17 of Oncotarget on August 14, 2026, titled “Systematic methodological flaws in DNA contamination assessment of mRNA vaccines: A critical analysis of Achs et al. (2025).”
The article was led by first and corresponding author Kevin McKernan from Medicinal Genomics, Beverly, Massachusetts, along with co-authors David J. Speicher from Cyrus Scientific Inc, Hamilton, Ontario, Canada, and Jessica Rose from Brownstone Institute, Austin, Texas.
Rather than presenting a new experimental vaccine analysis, the paper critically examines the methodology used by Achs et al. in a 2025 study that reported no excessive residual DNA impurities in COVID-19 mRNA vaccines. McKernan and colleagues argue that several methodological choices in that study could systematically underestimate residual DNA and therefore limit its suitability for regulatory safety assessment.
One major concern involves how quantitative PCR results were converted from DNA copy numbers into mass. Achs et al. used full-length plasmid molecular weight in their calculations even though their own sequencing data suggested much shorter median DNA fragment sizes. The critique argues that this approach requires fragmentation-correction factors because random DNA breakage can disrupt qPCR target regions and reduce the number of detectable amplicons. Without such correction, the authors contend that residual DNA mass may be underestimated.
The paper also highlights the importance of primer and amplicon design. Achs et al. used qPCR targets with substantially different amplicon lengths, including shorter kanamycin-resistance targets and longer spike-encoding targets. Because the reported median DNA fragment sizes were approximately 130–201 base pairs, longer amplicons would be less likely to remain intact after fragmentation. The authors therefore argue that this design could preferentially reduce detection of spike-associated DNA relative to shorter plasmid regions.
DOI - https://doi.org/10.18632/oncotarget.28913
Correspondence to - Kevin McKernan - Kevin.McKernan@medicinalgenomics.com
Abstract video - https://www.youtube.com/watch?v=xSWS3HDQUus
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Keywords - cancer, mRNA vaccines, DNA contamination, qPCR; plasmid DNA, RNA:DNA hybrids
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