I am an immunologist. I've been privileged to study the secrets of immunity and the power of vaccination at research centers in London, Cambridge, and Washington DC, and I'm keen to share them with a wider audience. My book, The End of Plagues: The Global Battle Against Infectious Disease, sets out to explore the universe of germs and the mysteries of immunity, explaining in everyday language the natural ways in which our bodies defend us against infection. Beginning with the discovery of smallpox vaccine, the book spans three centuries in pursuit of the story of vaccination as it spreads across the globe. It is a controversial story, peppered with crises, cliffhangers and dramatic shifts of fortune, and it leads at last to the global defeat of smallpox, the imminent eradication of polio, and a new war on tuberculosis, malaria, and HIV-AIDS. As individuals protected by immunization, as parents making crucial choices to protect our children, and as global citizens in a world which can defeat disease, we are all participants in this extraordinary story.