Properties and Behavior of Orally Administered Attenuated Poliovirus Vaccine

The main reason for the extensive investigation of the properties and behavior of various attenuated polioviruses was to determine whether and, if so, how maximally attenuated strains might safely be used for the production of long-lasting immunity and for the eradication of the naturally occurring virulent viruses. It is now evident that the capacity of polioviruses to produce harmless, immunogenic infections of the alimentary tract is not dependent on their neurotropic activity. The studies of several groups of investigators have also shown that such alimentary infections can be produced not only in people without antibody but in children with maternal antibody and in individuals with antibody resulting from the administration of Salk vaccine.1 Since the ingestion of attenuated strains has been found to reproduce the natural infectious process in the alimentary tract, there may be reason for expecting