| immune status of the population to poliovirus infection in singapore. | a seroepidemiological survey conducted after two decades of mass immunization against poliomyelitis in singapore showed a high level of herd immunity in the population to all three types of human poliovirus. neutralizing antibodies to poliovirus 1, 2 and 3 were detected in 93.9-96.7% of the population between 6 months and over 40 years old. adults above 30 years of age had a relatively high level of susceptibility to poliovirus infection, with 10.2-12% in the over-30-year age group possessing no ... | 1987 | 3034442 |