Review of use of inactivated poliovirus vaccine in campaigns to control type 2 circulating vaccine derived poliovirus (cVDPV) outbreaks.

Delivering inactivated poliovirus vaccine (IPV) with oral poliovirus vaccine (OPV) in campaigns has been explored to accelerate the control of type 2 circulating vaccine-derived poliovirus (cVDPV) outbreaks. A review of scientific literature suggests that among populations with high prevalence of OPV failure, a booster with IPV after at least two doses of OPV may close remaining humoral and mucosal immunity gaps more effectively than an additional dose of trivalent OPV. However, IPV alone demonstrates minimal advantage on humoral immunity compared with monovalent and bivalent OPV, and cannot provide the intestinal immunity that prevents infection and spread to those individuals not previously exposed to live poliovirus of the same serotype (i.e. type 2 for children born after the switch from trivalent to bivalent OPV in April 2016). A review of operational data from polio campaigns shows that addition of IPV increases the cost and logistic complexity of campaigns. As a result, campaigns in response to an outbreak often target small areas. Large campaigns require a delay to ensure logistics are in place for IPV delivery, and may need implementation in phases that last several weeks. Challenges to delivery of injectable vaccines through house-to-house visits also increases the risk of missing the children who are more likely to benefit from IPV: those with difficult access to routine immunization and other health services. Based upon this information, the Strategic Advisory Group of Experts in immunization (SAGE) recommended in October 2020 the following strategies: provision of a second dose of IPV in routine immunization to reduce the risk and number of paralytic cases in countries at risk of importation or new emergences; and use of type 2 OPV in high-quality campaigns to interrupt transmission and avoid seeding new type 2 cVDPV outbreaks.