The growing threat of wild poliovirus 1 and vaccine-derived cases in the COVID-19 era

Abstract

The detection of people with paralytic cases of wild poliovirus 1 (WPV1) in two African countries (ie, Malawi in February, 2022, and Mozambique in May, 2022) outside endemic areas of WPV1 transmission (ie, Pakistan and Afghanistan) will become a serious setback if low vaccination coverage and Comment www.thelancet.com/infection Vol 22 October 2022 1413 decreased surveillance of acute flaccid paralysis are not addressed with alacrity.Detection of vaccine-derived poliovirus (VDPV) outbreaks in new settings, including circulating vaccine-derived type 2 poliovirus (cVDPV2) in Ukraine in October, 2021, circulating vaccine-derived type 3 poliovirus (cVDPV3) in Israel in March, 2022, and cVDPV2 in the USA in July, 2022, and the environmental detection of VDPV in sewage systems in London, UK, in June, 2022, show the serious threat of polio reemergence in settings that had previously interrupted polio transmission.2,3 The COVID-19 pandemic has had a substantial role in diminishing the activities of national polio control programmes (eg, reducing their ability to conduct routine and supplemental immunisation activities and reducing acute flaccid paralysis surveillance).The WPV1 type that was identified in two people in Malawi and Mozambique in 2022 has been epidemiologically linked to a viral strain that was previously identified in Pakistan in October, 2019, emphasising the ease of importation of wild poliovirus or VDPV unless high vaccination coverage (ie, >95%) is maintained along with investigation of all cases of acute flaccid paralysis, environmental monitoring, and outbreak response plans...