Preston
MBow30 alt account
Original antigenic sin is a real problem that we may have to deal with. It exists with the flu. Basically your immune system is imprinted with the first exposure you have to a pathogen, whether it's through vax or infection. So basically you keep making immune responses aimed at the og strain or variant even when you're exposed to different strains/variants later in life. This doesn't ENTIRELY prevent new primary responses against OTHER parts but it's possible those responses get slowed or are weaker. So for example, for HL, she would probably kick the shit out of Alpha-like variants better than us. Or at least her immune system would recognize it better than us and work faster to fight it.
I recall reading something a while back that during one of the flu pandemics the older folks did quite well and the younger folks did poorly. This was because the flu was quite similar to one of the flu strains that many old folks were exposed to very early in their life. So through Original Antigenic Sin, they were able to fight it off far better than young folks. It's kinda interesting and can work as a blessing too sometimes. It's luck of the draw largely, though it may limit true robust broad-level protection in some regard.