“…This represented a more than 95% decline in the incidence of disease from the previous 5-year period (Berkovich et al, 1961). In these clusters, more than 50% of the subjects had received three or more doses of IPV (Berkovich et al, 1961;Gresham et al, 1962). The death rate from poliomyelitis had declined to 0.1 in 100,000 in 1961 compared with an annual death rate of 1.9 in 19151.9 in -19241.9 in , and 1.2 in 19451.9 in -19541.9 in .…”