The author studied the incidence of enterovirus excretion in 2 groups of children aged between 1 and 4 years, who had been given varying doses of Sabin polio vaccine. In the first group faeces were collected 60 days and in the second group 15 days after the last dose of vaccine had been given. In the first group 12,12% yielded poliovirus and 13,63% yielded "other enteroviruses"; in the second group the percentages were 37,61% and 9,17%. In both groups all three serological types of poliovirus were isolated. The previous vaccination status of the children in both groups, whether vaccinated with two or less or three or more doses, did not have a statistically significant effect on the subsequent virus isolations. The strains of poliovirus isolated were examined by the RTC40 and dextran markers. Of the 8 strains isolated from the first group 6 were identified as intermediate strains and 2 as wild strains. These 2 were isolated from the only 2 children who had received no vaccine at all. Of the 41 strains isolated from the second group 8 were intermediate and the rest were typical vaccine strains.
