(Not the one you responded to) I know what an mRNA vaccine is and the only clearcut answer is that "yes, obviously the long-tail risks of mRNA vaccines could outpace the long-tail risk of COVID-19". The statement is also true when you say "...COVID-19 could outpace...mRNA vaccines" as well, if that's not clear.

BTW the "long tail" of COVID-19 in children is totally unproven and the whole "long haulers" phenomenom is likely (a) a small part normal post-viral fatigue which we see with basically any virus, and (b) mostly psychosomatic/psychogenic illness.