Three years is the expected maximum effectiveness of the vaccine requiring re-vaccination. I interpret that as the mRNA significantly breaks down or is otherwise eliminated in three years.
Thanks for the explanation. You seem to think that it is important for the mRNA to be eradicated from the body down the road by the immune system attacking mRNA cells. If you never encounter Covid, would the same thing happen? Or will it just remain in the system, potentially causing problems? Note: I am not much of a scientist.