SERODIFFERENTIATION OF TYPE 3 POLIOVIRUS STRAINS ISOLATED 1960–1965 FROM PATIENTS AND HEALTHY VACCINEES

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Abstract
Eightyfive field strains of poliovirus were classified as vaccine-like or nonvacaine-like by serodifferentiation tests. The strains were differentiated on the basis of NK values (kinetics of neutralization) obtained with antisera of the vaccine strain (12a1b) and of field viruses. Forty field strains isolated from individuals with recent contact with oral polio type 3 vaccine were vaccine-like. Only one wild strain was similar to the vaccine strain. In virus isolates recovered over periods of one to 16 weeks from patients with recent contact with the vaccine virus and from healthy vaccinees, a slight antigenic drift was suggested in a few cases. Results of reciprocal serodifferentiation tests useful in revealing degrees of relationship to vaccine or wild strains suggested a wide variation in antigenic characters among nonvaccine-like wild strains. In contrast, with vaccine-like strains isolated from persons with no known contact, with recent vaccination, or with household contact, the data indicated that they belonged to a relatively homogeneous group. In 7 cases with paralytic poliomyelitis or encephalitis that occurred after vaccination or household contact with vaccine virus, the results indicated that in 2 the virus isolated was not progeny of the vaccine strain but related to wild viruses; in 3 with household contact, vaccine-like virus was isolated and in 2 with vaccination 3 to 4 months preceding onset of illness, vaccine-like polio type 3 virus was isolated from spinal fluid. The findings are discussed in relation to polio immunization.