Does Ipv Boost Intestinal Immunity Among Children Under Five Years of Age? An Experience From Pakistan

The OPV is the vaccine of choice in polio eradication, especially in developing countries, as it has eliminated the wild poliovirus type 2. However, the immunity induced by IPV is better than that induced by the OPV. The present study compared the mucosal and humoral response to poliovirus vaccines administered to previously OPV-immunized children to assess the immunity gap in children at-risk of high poliovirus transmission. This was a community-based three-arm cluster randomized controlled trial conducted from June 2013 to May 2014 in healthy children under five years of age living in three high-risk districts of Pakistan, i.e., Karachi, Kashmore, and Bajaur. 387 clusters were randomized (131 to arm A, 127 to arm B, and 129 to arm C); however, 360 remained in the trial until the end (116 in arm A, 122 in arm B, and 122 in arm C). These clusters were randomly allocated using a computer algorithm to receive routine polio program (bOPV) activities (control, arm A), additional interventions with community mobilization and provision of short-term preventive maternal and child health services and routine immunization, including bOPV via health camps, (arm B), or all interventions of arm B with an additional provision of IPV (arm C ~ bOPV and IPV). Blood and stool samples were collected from a sub-sample to estimate humoral and intestinal immunity. Study findings showed that the serum titers were highest in Group C (IPV+OPV) at the baseline for P1, where its increase over time was also more prominent. Titers for P2 and P3 were statistically significantly higher amongst those who had received a routine OPV dose versus those who had not; this was true for all study groups and visits. In populations with high Oral Polio Vaccine (OPV) failure rates, administering an Inactivated Polio Vaccine (IPV) booster after a minimum of two OPV doses may effectively bridge immunity gaps. The IPV alone offers limited benefits to humoral immunity and doesn't provide intestinal immunity to prevent the infection and propagation of live poliovirus among unexposed populations.