• Two types of living attenuated poliomyelitis virus were administered by mouth to 24 bottle-fed infants by adding the virus preparations to the formula. Sixteen received the SM strain (representing type 1), two received the TN strain (type 2), and six received both strains at different times. Ingestion of SM was followed promptly by an asymptomatic alimentary infection, demonstrated by isolating the virus from the feces. Repeated doses were necessary to establish the carrier state in three of these infants. Ingestion of TN by two infants was followed similarly by the isolation of type 2 virus from the feces. All infants developed active immunity after the inapparent alimentary infection. It was found safe to administer the virus to infants less than a month old. Two infants who had not received the virus were placed in cribs between those of other infants carrying SM but did not contract the infection. The presence of homotypic antibodies congenitally acquired from the mother did not prevent an active response in infants who received an adequate amount of virus.
Koprowski H, Norton TW, Hummeler K, Stokes J, Hunt AD, Flack A, Jervis GA. IMMUNIZATION OF INFANTS WITH LIVING ATTENUATED POLIOMYELITIS VIRUSLABORATORY INVESTIGATIONS OF ALIMENTARY INFECTION AND ANTIBODY RESPONSE IN INFANTS UNDER SIX MONTHS OF AGE WITH CONGENITALLY ACQUIRED ANTIBODIES. JAMA. 1956;162(14):1281-1288. doi:10.1001/jama.1956.02970310009003