1. Has positive antibody correlation tied to immunity been totally debunked?
2. Is it fair to assume the vaccine antibodies are equivalent to covid antibodies, in terms of immunity likelihood?.
Vaccine antibodies and covid antibodies have the same structure, so the lab test that measures spike protein does not differentiate between them.
Somebody who has been vaccinated and somebody who has had covid both seem to have immunity to covid for at least three months, based on the results of clinical trials.
Even if something isn't completely proven, I think it's understandable for it to be taken into account if there's a high likelihood of correlation. An example would be the vaccine itself. You write "You should assume that you don't have complete immunity until 2 weeks after the second dose." If we were to only trust 100% proven data, we would not assume immunity even 2 weeks after the second dose, as it's only shown a 95% likelihood of immunity.
Well, 2 weeks after the second dose we're 100% certain that you'll have 95% immunity...
But seriously, immunity isn't an on-off thing, like a light switch, but more like the sliding scale for brightness on your computer monitor, which gradually gets brighter and brighter. So you're right, that on Purim, 5 days after your second dose, you'll be further along on that sliding scale, and close to what's considered maximal immunity.
I've been taking all of the precautions all along, and I plan to, at least somewhat, through Purim - but I still feel that knowing the odds that I'm immune will help me to know just how concerned I should be..
Depends what you mean by "concerned".
Does knowing the odds mean that you'll be less anxious, better able to concentrate on the megilla, have a more relaxed seuda with family? Then, yeah, the odds that you're immune are pretty high.
Does knowing the odds mean that you'll be less likely to wear a mask, socially distance, more likely to dance and drink? In that case, it's better to assume that you're not yet immune.