Ring vaccination: The vaccination of all susceptible individuals in a prescribed area around an outbreak of an infectious disease. Ring vaccination controls an outbreak by vaccinating and monitoring a ring of people around each infected individual. The idea is to form a buffer of immune individuals to prevent the spread of the disease.
Ring vaccination was used to control smallpox until the last naturally occurring case in 1977. When an infection was diagnosed, all people who were or may have been exposed were identified and vaccinated. Then, a second "ring" of people who may have been exposed to the first ring were also identified and vaccinated. Ring vaccination was also recommended by the American academy of Pediatrics in 2002 for smallpox, should there be another outbreak (from terrorism or whatever). Ring vaccination has been used successfully as a disease-control strategy under other circumstances, for example, to contain foot-and-mouth disease in livestock in the UK. Also known as surveillance and containment.