Why don't we use antibody testing in conjunction with vaccines?
Our goal is to build herd immunity. If you test positive for antibodies, then you should move to a latter vaccine tier. For instance. If you are a medical worker that has antibodies already. Then you might get vaccinated later with a lower risk group. Or. If you tested positive for covid-19 currently or in the past 6 months and had no major symptoms, you might be moved to get vaccinated with a lower risk group.
We should also consider interactions. If you can avoid interacting with people, then you should not be a high priority to vaccinate. With the stipulation that you would be assisted in helping limit interactions.