Variations in the Responses of Infants to Living Attenuated Poliovirus Vaccines

LIVING poliovirus was adapted for use as an immunizing agent a decade ago1; since then there have been an increasing number of studies to determine the action and the most efficacious use of attenuated poliovirus, especially in infants. It was first shown in 1956 that infants can be actively immunized with living attenuated poliovirus vaccine given orally, even while they still have passively acquired maternal poliomyelitis antibodies; these observations were subsequently confirmed.2 3 4 5 However, after it was found that infants less than two or three months old do not seem to be as readily infected with attenuated poliovirus as older . . .