Characterization of poliovirus isolates in Japan after the mass vaccination with live oral poliomyelitis vaccine (Sabin).

From 1962 to 1968, 127 poliovirus isolates (92 from clinical specimens and 35 from healthy subjects) were subjected to intratypic serodifferentiation by the modified Wecker and McBride techniques. The two techniques gave concordant results for 103 strains, 91 of which were classified as vaccine-like, 9 as nonvaccine-like, and 3 as intermediate; 20 were classified as vaccine-like by one technique and as intermediate by the other, and 4 as nonvaccine-like by one technique and as intermediate by the other. The origin of the nonvaccine-like strains is unknown, but it is unlikely that they had been circulating in the community long. An rct/40-marker test of the isolates revealed a higher positivity rate than that found in field trials of Sabin vaccine. The results indicate that wild poliovirus has been almost completely eradicated from Japan.