I was just educated by my physician about some details of the differences between the qualitative and the semi-quantitative COVID-19 antibody tests. I understand now that the result of the semi-quantitative test is not an accurate indicator of the level of immunity that you may (or may not) have, and therefore should not be used by those who have had the disease as a determinant to decide whether or not to get vaccinated.
(As a side note, for someone who has had COVID-19 already, this means that the Qualitative anti-body test is completely pointless. All is does is tell you what you already know - that you have had COVID-19)
My physician explained to me that the antibodies in your blood (whether they are from a prior infection or induced by the vaccine), are not what actually fights the virus. It is the white blood cells that fight the infection by attacking the virus. He explained that the white blood cells are what actually produce the various types of antibodies, and that the "antibodies attach to the viruses and make them attractive targets for the white blood cells."
My question is this: Obviously, if the white blood cells are what fights the virus infection, and they are modified/tuned/adjusted in some way to recognize or react more to a specific pathogen, why don't we produce a test that measures the amount of white blood cells that have been so tuned to the COVID-19 viral signature? Is this because the white blood cells are not adjusted in any way, that the antibodies which are chemically "tuned" to recognize the COVID-19 viral signature, and which attach themselves to invading COVID-19 viruses, are what the white blood cells are attracted to ?
But if that is the case, then why is the level (in the blood), of these specific COVID-19 antibodies not a reliable indicator of the ability of the immune system to fight COVID-19 infection?