Clinical Investigations on Attenuated Strains of Poliomyelitis Virus

• Alimentary infection without acute disease and without neurological manifestations was induced in two series of human subjects. In one series, SM type 1 poliomyelitis virus was given in capsules; in the other, TN type 2 virus was given in milk suspension. Altogether, 225 nonimmune subjects have received one or the other of these two viruses for immunization purposes; all have developed antibodies, and none have suffered any ill-effects that could be ascribed to the ingestion of the living poliomyelitis virus. Within the isolation unit, observations on transmissibility of the virus were made by setting up conditions that permitted contact. Transmission occurred in 5 of 15 contacts. The nurses who cared for these patients showed no evidence of alimentary infection. When the viruses were administered simultaneously, the type 1 virus alone produced antibodies unless type 2 was given first or in larger amounts. Mercurous chloride and other drugs intended to suppress fecal excretion of the virus had little effect. Administration of gamma globulin at the time the virus was ingested had no effect on the antibody response.