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IN THE absence of enteric infection with other viruses, the feeding of a single type of live poliovirus vaccine to children who have not previously been infected with the same type of poliovirus usually results in viral multiplication in the intestinal tract, antibody formation, and complete or partial resistance to reinfection. The use of live poliovirus vaccine in areas with climatic and hygienic conditions which permit extensive dissemination of naturally occurring polioviruses and other enteric viruses throughout the year has been complicated by the problem of viral interference,1which we have attempted to overcome by the tactics to be described in this communication. The studies of one of us (M.R.-A.) and associates2in Mexico and of Plotkin and Koprowski3in the Belgian Congo have shown that vaccination programs in large subtropical or tropical cities that are spread out over a period of many weeks and include only
A. B. Sabin (Fri,) studied this question.