In all of your comments here you're being pretty ridiculous - you've read some books and articles, but are painting stories here in such a credulous fashion that makes me think you haven't actually done much work with cells and viruses. I was a genetic engineer for 20 years and engineered plenty of viruses for therapeutics, including plenty of retroviruses.

The existence of reverse transcriptases in nature does not imply that there's a plausible path to an mRNA vaccine reverse transcription event, even the presence of a known reverse transcriptase in say, an HIV infected cell - they'll have radically different priming systems, etc.

We have plenty enough evidence for core molecular cell biology processes to call out some ideas as radically improbable.