The Spread of Living Attenuated Strains of Polioviruses in Two Communities in Southern Louisiana

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Abstract
Living, attenuated polio-virus type 3 (Sabin vaccine) was administered orally early in June to all children in a group of families in 2 lower economic Negro communities in southern Louisiana which prior serologic study had been shown to lack widespread natural immunity to this virus type. At the same time, in a group of similar control families a placebo material was fed. Study of frequent, routine fecal specimens from all children served to indicate primary and contact infections. Excretion of homologous virus occurred in 90% of vaccine-fed children, and in 39% of contact children during the succeeding 7 weeks. Many concurrent "wild" enterovirus infections were detected. The failure of the vaccine strain to infect a larger proportion of the contact children was attributed in part to viral interference and in larger part to a lower infectiousness of the vaccine strain as compared with "wild" polioviruses. No illness of any sort could be associated with primary or contact poliovirus infection.