Excretion of live attenuated polioviruses in the faeces of orally vaccinated children. Comparison of two immunization schedules.

The excretion of live, attenuated poliovirus vaccine strains was determined in the feces of Prague Infants home children given 10(5) PFU of type 1 and 2 and 2.10(5) PFU of type 3 vaccine in a routine annual mass campaign. The first two faeces specimens examined in each vaccinee prior to immunization were negative for the virus. A total of 476 stool specimens were collected from 37 children at weekly intervals for a period of 18 weeks. The presence of type 1 poliovirus in the faeces of children given monovalent type 1 vaccine was detectable for 9 weeks, with a maximum in first week, and the virus was isolated in 74.2% of vaccinees. The timing of bivalent type 2 and type 3 vaccine was 9 weeks after monovalent type 1 immunization. The excretion of these two types of poliovirus was found to persist for at least 6 weeks. Type 2 poliovirus was isolated in all vaccinees, type 3 in 70.4% of children. The highest percentage of children excreting type 2 poliovirus was recorded in the first week, the excretion of type 3 peaked three weeks after bivaccine administration. The excretion peaks were reached relatively early postvaccination, with type poliovirus reaching the highest titre per 1 g of faeces. After revaccination (one year later) with monovalent type 1 vaccine, the vaccine strain of type 1 poliovirus could be detected for 6 weeks and was present in the highest percentage of positive stool samples.(ABSTRACT TRUNCATED AT 250 WORDS)