Immunologic memory induced at birth by immunization with inactivated polio vaccine in a reduced schedule.

One hundred forty-one healthy newborns were immunized 24 hours after birth with one dose of inactivated polio vaccine (IPV) of enhanced potency. Following the administration of a second vaccine dose six months later, a considerable proportion of babies responded with neutralizing antibody (NA) to the three poliovirus types. The very rapid occurrence and high antibody titer were indicative of an anamnestic response. Twenty-one infants who still had NA less than 1:4 to one-more poliovirus types after the second vaccine dose responded with very high NA values 7-10 days after a supplementary dose of IPV. It appears that IPV of enhanced potency administered at birth is apt to induce immunologic memory, which should provide the basis for protection against paralytic poliomyelitis in case of exposure to wild poliovirus later in life.