Some results of the work on mass immunization in the Soviet Union with live poliovirus vaccine prepared from Sabin strains.

In the course of campaigns for the mass immunization of large segments of the population of the Soviet Union with live poliovirus vaccine prepared in the USSR from attenuated Sabin strains, some 15 200 000 persons received oral vaccine in 1959 and over 77 478 800 persons (mainly between 2 months and 20 years old) in 1960. Approximately 95% of these were given the vaccine incorporated in dragées.The present paper gives data on the safety and immunological activity of the live vaccine, on virus carriage and transmission of the vaccine virus to contacts, and on virus interference.In a comparison between poliomyelitis incidence in 1960 in regions where mass live vaccine immunization had been carried out and the incidence in areas where inactivated Salk vaccine was used in 1958-60, it is shown that, while the Salk vaccine did not fundamentally influence the epidemic process, the Sabin live vaccine brought about a sharp reduction in incidence and prevented the usual summer-autumn rise in the number of poliomyelitis cases.It is concluded from the two years' experience in the mass use of live vaccine from Sabin strains that poliomyelitis epidemics can be prevented.