There is a theory that the mRNA sequences could have been reverse transcribed into the DNA of various organs, including liver cells.

https://www.mdpi.com/1467-3045/44/3/73/htm is a in vitro (but not in vivo) demonstration of one element of this theory.

Just for an example, acute organ damage doesn’t necessarily present symptoms immediately. I knew a kid who had a viral heart infection in his teens that severely damaged it. He recovered in the sense that he could mostly live normally, but his doctor told him he’d be lucky to live past 50.