Herd immunity (also called herd effect, community immunity, population immunity, or social immunity) is a form of indirect protection from infectious disease that occurs when a large percentage of a population has become immune to an infection, whether through vaccination or previous infections, thereby providing a measure of protection for individuals who are not immune. In a population in which a large proportion of individuals possess immunity, such people being unlikely to contribute to disease transmission, chains of infection are more likely to be disrupted, which either stops or slows the spread of disease. The greater the proportion of immune individuals in a community, the smaller the probability that non-immune individuals will come into contact with an infectious individual, helping to shield non-immune individuals from infection.

In the present book, fifteen typical literatures about Herd Immunity published on international authoritative journals were selected to introduce the worldwide newest progress, which contains reviews or original researches on Herd Immunity, infectious disease and immunity, etc. We hope this book can demonstrate advances in Herd Immunity as well as give references to the researchers, students and other related people.