Any pointers to reading material on the detection process? A web search found this article.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6791314/

> Given the central role of RNA in many fundamental biological processes, including translation and splicing, changes to its chemical composition can have a detrimental impact on cellular fitness, with some evidence suggesting that RNA damage has roles in diseases such as neurodegenerative disorders. We are only just beginning to learn about how cells cope with RNA damage, with recent studies revealing the existence of quality-control processes that are capable of recognizing and degrading or repairing damaged RNA.

That article discusses RNA not mRNA (messenger RNA). mRNA is used by ribosomes to "print" proteins. Totally different thing.

How does it recognize corruption? Certainly some could be processed with incomplete or incorrect results. It's really hard (probably impossible) to show that there will not be negative effects from that.

Valid mRNA has a start codon and a stop codon. Without these mRNA will be broken down and untranslated. However without translation the vaccine will be useless. So while unintended translation is unlikely it is possible that efficacy would be impacted.

How do we guarantee that? Is there a biological equivalent of a checksum?

You have trillions of mitochondria. Do you think there is no error correction present?

(The actual estimate is 10 million billion...)

Edit following my other edit: each cell has something like 10 million ribosomes.

NMD does similar work, but not in a checksum-like way.

https://en.wikipedia.org/wiki/Nonsense-mediated_decay