a1 Smallpox Eradication Unit, World Health Organization, 1211 Geneva 27, Switzerland
a2 John Curtin School of Medical Research, Australian National University, GPO Box 334, Canberra, Australia
The eradication of smallpox was achieved by surveillance and containment vaccination after the failure of mass immunization campaigns. The reasons for this failure are considered in this paper. Comparison of population densities in the Indian subcontinent and Africa show that in highly populated areas even an 80% vaccine coverage will still leave a density of susceptibles high enough to maintain the disease, a finding with important implications for other vaccine campaigns.
(Received May 15 1985)
(Accepted January 10 1986)