In 1988, the World Health Assembly declared WHO’s commitment to global eradication of polio by 2000. But in 1993, the goalpost was shifted — the goal was to eradicate only wild poliovirus globally by 2000. That meant that eradicating vaccine-derived poliovirus (VDPV) and vaccine-associated paralytic poliomyelitis (VAPP) was no longer the objective. The reason: developing countries using oral polio vaccine reported many vaccine-derived or vaccine-associated polio cases annually. Meanwhile, the developed countries switched to inactivated polio vaccine thus eradicating polio decades ago.
Though the last case of type 2 wild poliovirus was reported in October 1999 from India (and declared eradicated globally in 2015), more than 90% of vaccine-derived poliovirus outbreaks are due to type 2 virus present in oral polio vaccines. Also, 40% of VAPP are caused by type 2 oral polio vaccine. Similarly, the last case of type 3 wild poliovirus was reported in November 2012 (and declared eradicated in 2019). But many cases of VAPP from type 3 virus occur in countries using oral polio vaccine.
Surprisingly, the Global Polio Eradication Initiative (GPEI) has never reported VAPP cases throughout the 34 years of polio eradication efforts. And the Indian government does not count VAPP as polio as such cases are sporadic and pose little or no threat to others.
