Smallpox Vaccination: The End of an Era

Abstract

Summary. In 1971 it wasrecommended that routine immunization against smallpox be discontinued in the United States. While smallpox vaccine has had a venerable record of disease control, deliberations which led to the reversal of the longstanding public health plicy reflect a reconsideration of smallpox status in the world. Smallpox was introduced into the western hemishere almost 450 yeas ago. Immunoprophylaxis was initiated in the United States more than 250 years ago. The record of smalpox vaccine is impressive. It may bbe credited with the reduction of cases in the United States from more than 110,000 in 1920 to an absence of cases since 1949. However, we cannot credit the continued maintenance of a smallpox‐free country to the routine use of vaccine and cannot credit the level of immunity of our population for the prevention of importations. The fact is that our “herd immunity” has not been challenged for 25 years.As the incidence of smallpox in the world has fallen, and with the disappearance of the disease altogether in the developed countries, the substantial toxicity of the vaccine began to stand out in bold relief. In the United States, 7–8 deaths attributable to complicatins of the smallpox vaccine occurred each year. In addition, significant nerrologic and dermal complications of the smallpox vaccine occurred each year. In addition, significant neurologic and dermal complications have occurred at the rate of 8,000 per year. These complications occurred among 5–6 million primary and 7–8 million revaccinees each year.The risk of importation of cases of smallpox in a given country is proportionate to the incidence of endemic smallpox in the world and the number of tramellers from endemic areas. World incidence of smallpox has fallen dramatically. As late as 1962, 61 countries reported smallpox. The current list includes only 4 countries where smallpox is endemic‐India, Pakistan, Bangladesh and Ethiopia. Exportations in the first portion of 1974 have been confined almost exclusively to adjacent land areas. Recently, the Americas, having gone without endemic cases for 2 years were declared disease free; Indonesia has recently received similar status.The success of recent control and eradication programs on a world‐wide basis is based upon a new understanding of smallpox epidemiology and a new and vigorous approach to its containment. Emphasis upon epidemiologic investigation of all suspected cases and systematic vaccination of contacts ha proved very effective. However, importations into non‐epidemic areas can theoretically occur as long as small‐pox exists anywhere in the world. Expericnce has shown that selective “ring vaccination” of contacts of such imported cases can effectively control spread. This policy plus continued vaccination of high risk individuals, i.e., health personnel and travellers to and from endemic areas, provides the least toll in morbidity and mortality. Continued active support is required for smallpox surveillance and eradication programs around the world.