Systematic analysis of COVID-19 mRNA vaccines using four orthogonal approaches demonstrates no excessive DNA impurities

Despite substantial evidence for benefits of vaccination in mitigating the COVID-19 pandemic, the use of mRNA vaccines faces skepticism built on coincidental health events occurring after vaccination without proven causality. One of the claims regarding excessive amounts of residual DNA from the vaccine manufacturing process has arisen from misinterpretation of improperly conducted analyses. Here, we assessed the quantity, quality and identity of residual DNA in mRNA vaccines based on thoroughly performed and properly interpreted orthogonal methods, including qPCR, fluorometry, capillary electrophoresis and short-read DNA sequencing. Our results show that the quantity of residual DNA in all 15 analysed batches of Comirnaty and Spikevax vaccines is below approved limits and that it consists of small fragments originating from the template used to transcribe mRNA during vaccine production. We demonstrate that reliable mRNA vaccine analysis for DNA impurities requires rigorous application of well-controlled methods that minimise mutual interference of vaccine components.