It is true that antibodies are not the whole story when it comes the the immune system. There are also T cells and B cells, which are not easily tested form=, b because they don't float around in your blood until your body is actually challenged by the disease, and then (hopefully) your body quickly mounts a response. That said, it is the ONLY way we have of checking the immune status of immune compromised people. While for people with normal immune systems, it doesn't make sense to test, they have found that it does make sense to test those of us who are immune compromised. Because people who are on one of the drugs I am taking are known to have responded poorly to the vaccine, and are known to have been getting sick and hospitalized, even after being vaccinated, my rheumatologist had me tested. After being fully vaccinated, your level of immunity should be at least 400 and can be up into the thousands. Mine was 24. Which is scarily low. According to one report I read, I am close to 500 times more likely to catch Delta than the average person, and have a bad outcome from it.I have been confused about the antibodies because there are news articles that say antibody testing isn’t a clear indicator of protection, but the recommendation to get a third vaccination is based on studies of antibody testing. Did you do the antibody testing through your doctor?