 The WPV2 virus was declared eradicated in September 2015 as it had not been detected in circulation since 1999 and WPV3 was declared eradicated in October 2019, having last been detected in 2012.Both types persist in the form of circulating vaccine-derived strains, the product of years-long evolution of transmissible oral vaccine in under-immunized populations.There were 37 reported WPV1 cases with an onset of paralysis in 2016, half as many as in 2015, with the majority of the cases in Pakistan and Afghanistan.