Commercial antibody tests DO NOT MEASURE the antibodies to the spike protein which is evoked by all three vaccines in current use in the USA.
This is a whole new COVID sideline - calls from vaccinated people who persuaded their PCP to order the (inevitably negative) COVID antibody test, and are calling because the vaccine “didn’t work”.
And while it is true that immunity rests in long-lived memory T cells, and it is also true that you can measure (count) a person’s TOTAL T cell numbers, it is extremely difficult, time consuming, and expensive to grow a person’s T cells in cell culture and then to test them for reactivity to any specific target.
I did T-cell transformations in a different life, and to do one patient takes a couple of weeks, minimum, assuming the assay works at all. So checking a person’s T cells for anti-SARS CoV 2 reactivity is not a feasible general use test to check millions of people.
There is a test for Covid specific T Cells. Costs about $150. Adaptive Biotechnologies. https://www.t-detect.com/
Maybe given your knowledge you can comment on the test. AB is a credible company. $150 for a test including the on site blood draw seems like something very different than what you are describing.
We routinely do Sars covid 19 ab on patients via LabCorp. Would you accept their results?