More great news in the world of polio eradication…

Polio vaccine Image/Michael Washington, PhD, Health Scientist, NCEZID
Polio vaccine
Image/Michael Washington, PhD, Health Scientist, NCEZID

Earlier this week it was reported that Nigeria has interrupted transmission of wild poliovirus and is no longer a polio endemic country. Now, in some belated news from the polio eradication front, the Global Commission for the Certification of Poliomyelitis Eradication (GCC) on Sep. 20 concluded that wild poliovirus type 2 (WPV2) has been eradicated worldwide. The last detected WPV2 dates to 1999, from Aligarh, northern India.

There are three wild poliovirus serotypes:  WPV1, WPV2 and WPV3. WPV3 has not been detected globally since November 2012 (in Nigeria); the only remaining endemic WPV1 strains are now restricted to the two remaining endemic countries, Pakistan and Afghanistan.

This declaration will support the final decision on whether the switch from trivalent to bivalent oral polio vaccine will be made as scheduled in April 2016, which will be decided by the Strategic Advisory Group of Experts on immunization next month.

The Global Polio Eradication Initiative (GPEI) says oral polio vaccines (OPV) contains attenuated (weakened) polioviruses.  On extremely rare occasions, use of OPV can result in cases of polio due to vaccine-associated paralytic polio (VAPP) and circulating vaccine-derived polioviruses (cVDPVs) like we’ve seen recently in the Guinea/Mali border area and Ukraine.

For this reason, the global eradication of polio requires the eventual cessation of all OPV.  With WPV2 transmission already having been successfully interrupted, the only type 2 poliovirus which still, on very rare occasions, causes paralysis is the type 2 serotype component in trivalent OPV.  The continued use of this vaccine component is therefore inconsistent with the goal of eliminating all paralytic polio disease.