On November 26, 2019 Dr Shiva Ayyadurai delivered a prestige lecture at NSF Science & Technology Center, Purdue University on the “Modern Theory of the Immune System” based on current science and his PhD work. The immune system is far more complex than the 1950’s Innate plus Adaptive parts that is the accepted model.
This knowledge will help your understanding of how natural infection builds broad-spectrum, long-lasting immunity against virus variants, compared to the narrow spectrum, waning immunity that a single-protein, antigen vaccine stimulates…but even that is a simplified explanation.