Why is it necessary to stop OPV use in routine immunization programmes, after the eradication of wild poliovirus?
A. After interruption of wild poliovirus globally, the Sabin strains contained in OPV will be the only source of live polioviruses in the community. OPV, in rare instances, can cause vaccine-associated paralytic poliomyelitis (VAPP). In addition, the Sabin strains can mutate back to greater neurovirulence and transmissibility, establish endemic and epidemic transmission, and thus pose a threat to eradication. The continued use of OPV after the interruption of transmission of wild poliovirus is therefore increasingly considered inconsistent with eradication. Polio cases due to vaccine-associated paralytic poliomyelitis (VAPP) and outbreaks due to circulating vaccine-derived polioviruses (cVDPVs) are the two main reasons for eventually stopping the use of OPV for routine immunization in all countries.
