HUMORAL AND MUCOSAL IMMUNITY IN INFANTS INDUCED BY 3 SEQUENTIAL INACTIVATED POLIOVIRUS VACCINE - LIVE ATTENUATED ORAL POLIOVIRUS VACCINE IMMUNIZATION SCHEDULES

The relative immunity induced by sequential administration of inactiva ted poliovirus vaccine (IPV) produced in human diploid cells and live attenuated oral poliovirus vaccine (OPV) was evaluated by randomizatio n of 510 infants to receive IPV and OPV sequentially according to one of three experimental schedules, IPV only, or OPV only. The antibody r esponse to two IPV doses was lower than expected. However, for each of the IPV-OPV sequential schedules, the first OPV dose significantly en hanced seroconversion rates and geometric mean microneutralization ant ibody titers. Three months after the final dose, 96%-99%, 99%-100%, an d 81%-100% of infants had antibodies to poliovirus types 1, 2, and 3, respectively, and subjects with two or more prior OPV doses were signi ficantly less likely than those with none or one prior OPV dose to exc rete virus in feces after an OPV challenge. Sequential IPV-OPV immuniz ation is now recommended for routine use in the United States. The opt imal schedule consists of two IPV doses followed by two OPV doses.