I mean, I guess my follow up question is... where does the reverse transcriptase come from? My understanding is that the mRNA, by itself, isn't a retrovirus capable of integrating itself with your DNA. It's not built for it. There's no mechanism for reverse transcription in the mRNA in the vaccines, and the mRNA doesn't go near the nucleus of the cell, instead swimming around in the cytosol until a ribosome picks it up.