Extremely sloppy Quality Control.
"We sequenced all the nucleic acids that were inside of the mRNA vaccines, and it's not what's on the label. Yes the vaccine mRNA we can see there, but 10-30% of the nucleic acids in there are DNA from the expression vector they used to make the RNA. That shouldn’t be present."
–Kevin McKernan, Former R&D, Human Genome Project, MIT
https://rumble.com/v2dpmxe-mrna-lipid-nanoparticles-and-more-scientists-join-april-moss.html