Impact of inactivated poliovirus vaccine on mucosal immunity: implications for the polio eradication endgame

Abstract

The polio eradication endgame aims to bring transmission of all polioviruses to a halt. To achieve this aim, it is essential to block viral replication in individuals via induction of a robust mucosal immune response. Although it has long been recognized that inactivated poliovirus vaccine (IPV) is incapable of inducing a strong mucosal response on its own, it has recently become clear that IPV may boost immunity in the intestinal mucosa among individuals previously immunized with oral poliovirus vaccine. Indeed, mucosal protection appears to be stronger following a booster dose of IPV than oral poliovirus vaccine, especially in older children. Here, we review the available evidence regarding the impact of IPV on mucosal immunity, and consider the implications of this evidence for the polio eradication endgame. We conclude that the implementation of IPV in both routine and supplementary immunization activities has the potential to play a key role in halting poliovirus transmission, and thereby hasten the eradication of polio.

Keywords:

• environmental surveillance
• eradication
• inactivated poliovirus vaccine
• mucosal immunity
• oral poliovirus vaccine
• poliovirus

Acknowledgement

The authors are grateful to Hannah Slater for providing valuable comments on the manuscript.

Financial & competing interests disclosure

E Parker is a former Assistant Commissioning Editor at Expert Review of Vaccines. E Parker and K O’Reilly receive funding from the UK Medical Research Council; N Molodecky is funded by the Bill & Melinda Gates Foundation; M Pons-Salort is funded by the Wellcome Trust (106073/Z/14/Z); and N Grassly is funded by the Bill & Melinda Gates Foundation (#OPP1099374), WHO (2013/363982) and UK Medical Research Council. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Key issues

• The induction of robust mucosal immunity is necessary to halt poliovirus transmission, and is therefore crucial to the success of the polio eradication endgame.

• Inactivated poliovirus vaccine (IPV) has long been thought to induce only limited mucosal immunity; however, it has recently been shown that the vaccine may significantly boost mucosal protection among individuals who have previously received oral poliovirus vaccine (OPV). This effect may exceed the boost in mucosal immunity induced by additional doses of OPV.

• It is now recommended that at least one dose of IPV be included in all routine immunization programs, and the vaccine will also increasingly be used alongside OPV in supplementary immunization activities conducted in polio-endemic countries. In both these contexts, the boosting of mucosal immunity by IPV may help eliminate poliovirus transmission.

• Following OPV withdrawal, environmental surveillance will be crucial for the detection of poliovirus circulation, owing to the potential for silent poliovirus circulation in populations immunized only with IPV.

Notes