Herd Immunity: A Brief Review.

Immunization is a means of protecting the greatest number of people. By reducing the number of susceptible in the community, it augments "herd immunity" making the infection more difficult to spread. It also reduces the risk for those individuals who have escaped vaccination or those who have not developed satisfactory protection. It is well to bear in mind that immunizations are not at all 100 per cent effective, particularly when an individual is exposed to a large dose of pathogenic organisms.