The immune system is central to human health. Growing understanding of the immune system, and especially the creation of immune memory (which results in long lasting protection), have led to major breakthroughs in medicine and the design of vaccines.

In this Very Short Introduction, Paul Klenerman describes the immune system, and how it works in health and disease. He considers how the immune system evolved, the basic rules that govern its behavior, and the major health threats where it is important. Paul Klenerman also explains how things can go wrong when there is too little or too much immunity. The book also addresses what we learned about the immune system from the COVID-19 pandemic and how that has influenced thinking about future pandemics.