The story begins with Kevin McKernan, a scientist with 25 years experience in the genomic field and a leading expert in sequencing methods for DNA and RNA. He has worked on the Human Genome Project and more recently in medicinal genomics involving DNA sequencing. In the process of trying to sort out a sequencing problem, McKernan used anonymously sent, Pfizer and Moderna Covid-19 bivalent vaccines to act as mRNA controls.

…what we discovered in the process is that they weren’t pure mRNA. They actually had a lot of DNA in the background.’ So, the Pfizer and Moderna vials of bivalent vaccine that McKernan tested were contaminated with DNA.  DNA encoding the spike gene and potentially capable of inserting into the genome of an organism.

https://brownstone.org/articles/vax-gene-files-accidental-discovery/?