What is herd immunity?

Community Immunity. When a critical portion of a community is immunized against a contagious disease, most members of the community are protected against that disease because there is little opportunity for an outbreak. Even those who are not eligible for certain vaccines—such as infants, pregnant women, or immunocompromised individuals—get some protection because the spread of contagious disease is contained.
Protecting everyone. Herd immunity or " community immunity" is a term describing where the majority of individuals have been immunized against a specific infection.Thus there are very few people able to be infected starting the chain of transmission.The harder it is to start a community infection, the fewer people who get sick.So immunization protects not only individuals, but their neighbors too.