Age- and dose-interval-dependent antibody responses to inactivated poliovirus vaccine

Antibody responses were studied in five groups of children immunized with d ifferent three-dose schedules of inactivated poliovirus vaccine (IPV). The age of the chi Id at the fi rst dose (1-4 months) and the interval between the first and second doses (2-4 months) influenced the initial responses in a serotype-dependent manner. All the groups attained sufficient antibody l evel after three doses but the third dose given at 18 months resulted in hi gher persisting antibody levels than that given at 12 months. The highest p ersisting antibody titers against PV1 and PV2 (but not against PV3) at the age of 3 years were measured in the control group immunized with the curren t schedule (P < 0.001) in which the first dose is given at 6 months. The le vel of maternal antibodies present at the time of the first dose correlated negatively with the antibody titers as late as at 3 years of age. It is co ncluded that three doses of IPV given in widely variable schedules may resu lt in satisfactory immune responses in children but, for optimal results, v ery early onset of the program and short dosage intervals should be avoided . (C) 2001 Wiley-Liss, Inc.