mRNA doesn't change your genetic sequence in any way. It is the exact same intermediate - and temporary - kind of material that your cells generate internally all the time as part of your normal cell processes The m in mRNA stands for messenger. I'm failing to find anything I consider to be a succinct explanation in layman's terms (other than the one in the piece under discussion: all that the mRNA vaccines do is to…
Not exactly. The mRNA fragments are instructions to build pieces of the virus. Your cells execute the mRNA instructions, build virus fragments, and _then_ the immune system notices all these unknown fragments and learns how to destroy them.
Then next time around B-cells and T-cells are primed from all this target practice and its a lot easier, even if the neutralizing antibodies wane.