1 Department of Pediatrics, The University of Texas Health Science Center 7703 Floyd Curl Drive San Antonio, TX 78284
The objective of immunization is to reduce morbidity produced by natural illness. Ideally, we would like to eradicate natural infection. This goal, which has been presumably accomplished for smallpox, has clearly eluded us in the case of measles. Eradication requires reduction in the number of susceptible subjects to the point where transmission of natural infection is interrupted. It is clear in the case of measles that we continue to have pockets of susceptible subjects that permit perpetuation of this disease. Clusters of cases occur in neighborhoods where immunization levels are low and in situations where susceptible subjects are brought together in close contact, such as in high schools, colleges, and military installations.