A worldwide shift in polio vaccines for routine immunisation

The world is now closer to global polio eradication than ever before. In 1988, when the World Health Assembly set its sights on complete eradication of polio, an estimated 350 000 paralytic cases occurred and 125 countries were considered endemic. In 2015, only 39 cases have been detected in two countries (as of Sept 8, 2015).1 At present, only wild poliovirus type 1 is known to be circulating. The last outbreak of naturally occurring type 2 wild poliovirus occurred in 1999, and type 3 wild poliovirus has not been detected since 2012. As naturally occurring poliovirus cases decrease, paralysis induced by vaccine-related viruses in oral poliovirus vaccine (OPV) such as vaccine-associated paralytic poliomyelitis (VAPP) and circulating vaccine-derived polioviruses (cVDPV)2 continue to occur, although in small numbers. Thus, for the world to be truly free from polio, all three wild poliovirus serotypes must be eradicated and use of OPV must stop.