I’ve read where there was talk about putting some sort of coding in the vaccine to show you’ve been vaccinated, actually a tracker.
They need to explain the specific mechanisms. An electronic ID at any distance, more than a fraction of an inch, is about 1/2 in size. Non-electronic is plausible, some sort of chemical they add and then do a long distance MRI-type scan to detect it. I have never heard of such a thing, but it's possible.
My experience with electronics including the smallest possible powered chips, is that an ID will not be electronic.