Assessing the immunogenicity of three different inactivated polio vaccine schedules for use after oral polio vaccine cessation, an open label, phase IV, randomized controlled trial

BACKGROUND: After global oral poliovirus vaccine (OPV) cessation, the Strategic Advisory Group of Experts on Immunization (SAGE) currently recommends a two-dose schedule of inactivated poliovirus vaccine (IPV) beginning ≥14-weeks of age to achieve at least 90% immune response. We aimed to compare the immunogenicity of three different two-dose IPV schedules started before or at 14-weeks of age. METHODS: We conducted a randomized, controlled, open-label, inequality trial at two sites in Dhaka, Bangladesh. Healthy infants at 6-weeks of age were randomized into one of five arms to receive two-dose IPV schedules at different ages with and without OPV. The three IPV-only arms are presented: Arm C received IPV at 14-weeks and 9-months; Arm D received IPV at 6-weeks and 9-months; and Arm E received IPV at 6 and 14-weeks. The primary outcome was immune response defined as seroconversion from seronegative (