A few months ago, I wrote an article on delayed immunity. The term for that is anamnestic response. Antibodies represent immediate immunity. At that time most people were not talking about antibodies from COVID immunization. That is now the case. So a refresher appeared to make sense. When we have an infection we develop antibodies. After the infection the antibody levels can be measured. That is how we typically determine if people remain protected against the illness. If antibodies are present, the patient is protected. Those antibodies are produced by one type of immune cell. For example a study has looked at antibody levels in humans who have had hepatitis B vaccine in infancy. At the 20-year point only 37 percent of them still had measurable antibody levels. They were then given an additional dose of the vaccine and checked. This was done to look at the function of the second group of immune cells in the body. This group of cells does not put out antibodies on a regular basis. However, they have a memory for previous infections. All patients, regardless of antibody levels, poured out a huge number of antibodies to the infection into the bloodstream [...]