What is the best way to measure rates of covid immunity?

In my previous post on the covid pandemic I mentioned that the body’s main defence against viruses is T-cells, not antibodies, and that the only reason we test for antibodies instead in clinicial practice is because it is easier and cheaper. I also ventured a hypothesis that the levels of population immunity are much higher than is being found in the antibody tests, and that this is because lots of people who don’t have antibodies do have covid specific T-cells. It turns out that this hypothesis is supported by new evidence. read more