The mRNA is translated by ribosomes into proteins. A single strand as long as it keeps finding ribosomes can produce multiple copies of a protein. mRNA half life vary from minutes to hours. I don't know the estimated half life of the vaccine mRNA is. But since it's not being manufactured by the cell it would likely be completely gone in hours to a couple of days even if the cell it was in was still alive.
To turn the mRNA into DNA you would need certain mechanisms in place like you would find in a retrovirus, which is able to make a cell use RNA to manufacture another copy of the virus. I don't believe anything like that is being employed in the vaccines
to get into the nucleus the mRNA would have to be coated with certain proteins so the nucleus recognizes it and pulls it in through one of its pores. I haven't seen any information that the vaccine mRNA are coated with protein to get into the nucleus of a cell. But I haven't read all the technical papers on the subject.
Aha Thank you. I was going to ask about a half life. That makes sense now that it could not reproduce an effective lasting strand.
Also I was wondering how the DNA would accept a strand that would introduce a foreign strand without rejecting it outright.
Your posts and another FReeper had me pulling books off shelves last night.