Herd immunity is the protection from an infectious disease that occurs when a population is immune either through vaccination or immunity developed through a previous infection. If a country or area has herd immunity to a disease, it means a large proportion of that community becomes immune to the disease. Herd immunity makes the spread of the disease from person to person less likely.
This is a companion discussion topic for the original article at https://patient.info/news-and-features/covid-19-what-is-herd-immunity-and-will-we-ever-reach-it