we still need the primary antibody count up high, because we’re still in a pandemic, thus the desire for boosters.
in both vaccine induced and survivor induced immune responses, long term immune systems come online to store a memory of the disease so that on future challenge, more of those antibodies will be produced by people fairly rapidly after future exposure, even when your blood stream isn’t full of covid antibodies anymore.
When there are this many cases floating around, though, you can't afford to wait for the spin-up time.
If i'm asking for the same image every 500ms from your webserver, do you want to go to disk every damn time, or are you gonna cache it? Same deal, kinda.