Adults who are immune and protected from polio nevertheless can, and do, get reinfected with wild polioviruses and become part of transmission chains.

Circulating vaccine-derived polioviruses are wild-like, and adults may get infected and continue transmitting them to children.

As the primary source for reinfection in adults are first-time infected infants and children, additional doses of inactivated poliovirus vaccine for children will help to interrupt all transmission chains and accelerate polio eradication.

Every communicable disease results from 3 events: pathogen amplification, pathogen transmission, and host-pathogen interaction.1 While disease is overt, pathogen amplification and transmission are covert, discernible through epidemiological investigation. Disease can be prevented in the individual by immunization, resulting in drastic alteration of host-pathogen interaction. For disease elimination/eradication, a vaccination program’s strategy must be designed not only to protect all individuals from disease but also to interrupt all transmission chains.2

In 1988, poliomyelitis (polio) was targeted for eradication by the year 2000.3 Wild poliovirus (WPV) is an exclusive human pathogen, amplification occurring in infected individuals. However, the transmission dynamics of WPV have not been adequately investigated to explain the main chains of transmission.

Many global polio experts believe in the superiority of live oral poliovirus vaccine (OPV) over inactivated polio vaccine (IPV) for stopping the spread of poliovirus in the community,4,5 reasoning that only OPV induces secretory immunoglobulin A (IgA)-mediated mucosal immunity. Nonetheless, the intriguing phenomenon of continued virus circulation—WPVs until 2012 and overwhelmingly circulating vaccine-derived polioviruses (cVDPVs) since then— despite years of heavy vaccination pressure with OPV demands an explanation.

All immunization activities of the Global Polio Eradication Initiative are in children aged younger than 5 years. In low- and middle-income countries (LMICs), they get many doses of OPV, and only in some countries, just 1 or 2 doses of IPV. Do …