Effect of Sabin Poliovirus Vaccine on Incidence of Poliomyelitis in Italy

Extensive use of poliomyelitis vaccine (Salk) from 1958 to 1963 did not prevent the annual occurrence of thousands of paralytic cases of poliomyelitis in Italy. After the mass use of live oral poliovirus vaccine (Sabin) early in 1964, the number of reported cases quickly dropped from an average of more than 3,000/year during the four years prior to the use of oral vaccine to 254 in 1965, 147 in 1966, 106 in 1967, and 87 in 1968, and at least a portion of the reported cases could not be confirmed as having been caused by polioviruses. Most of the remaining cases of poliomyelitis have occurred in the southern and island regions (1.17/100,000 vs 0.08 in northern and 0.009 in central Italy in 1965; 0.68/100,000 vs 0.04 in northern, and 0.06 in central Italy in 1966) where the percentage of children vaccinated during the initial campaign and in the ongoing programs was, until recent compulsory vaccination legislation, much less than in the northern and central regions of the country.