I think that part of the problem is that scientific studies may have several "endpoints" in mind that they want to study.
For example, one study might have the following endpoints:
1) Did the person develop COVID-19 symptoms?
2) Did the person test positive for COVID-19?
3) Was the person hospitalized?
4) Did the person die of (or with) COVID-19?
Each of such endpoints must be clearly defined so that determinations can be made unambiguously.
As for "immunity", I don't think I have seen claims of such in what I have read. I have read that there is concern that vaccinated people may still acquire and spread COVID-19.
My plan (if Sutter ever re-schedules the appointment that they cancelled for today) is to continue staying away from unvaccinated people. I'm friend to a couple who are 87 and 89. They haven't had a first dose yet and I would not want to be the cause of their demise.
Your right on the end point percentages. They are actually saying (the full dosage) gives 100% immunity from hospitalization or death (unless the vaccine kills you, that’s a different end point)