I finally got a good answer (IMO) regarding antibody levels, boosters/etc. as it pertains to COVID and the vaccines.
It starts around 22 minutes. He's interviewing Dr. Offit from the FDA Vaccine Advisory Committee. I thought he explained it (again, at least for me) quite well. Unfortunately I don't think (just my opinion) the powers that be (at least here in the US) follow this, and will probably mandate boosters every 6 months, as they seem to rely only on antibody levels. Hopefully I'm wrong (as Dr. Offit points out, "we" have never done this for any other virus in terms of boosters for simply antibody levels when we have good memory B/T-cell measures).