Update on Vaccine-Derived Poliovirus Outbreaks — Worldwide, July 2019–February 2020

Mary M. Alleman, PhD; Jaume Jorba, PhD; Sharon A. Greene, PhD; Ousmane M. Diop, PhD; Jane Iber, MSc; Graham Tallis, MBBS; Ajay Goel, MSc; Eric Wiesen, MS; Steven G.F. Wassilak, MD; Cara C. Burns, PhD


Morbidity and Mortality Weekly Report. 2020;69(16):489-495. 

In This Article


After outbreak detection, prompt and effective mOPV2 vaccination of children will interrupt cVDPV2 transmission and limit emergence of new VDPV2 strains in outbreak response zones. Although many previously identified cVDPV2 outbreaks have been interrupted or controlled as forecasted,[1–4] GPEI has been challenged by the increased number of outbreaks from newly seeded VDPV2 emergences during January 2018–February 2020, following mOPV2 SIAs that did not reach sufficient coverage; in addition, there are protracted cVDPV2 outbreaks from prior emergence that have not been successfully controlled for the same reason.[1–4] In areas where no mOPV2 has yet been used, approximately four birth cohorts that are fully susceptible to mucosal poliovirus type 2 infection have accumulated since the April 2016 tOPV-to-bOPV switch.[1,2,4]

The utility of environmental surveillance to complement AFP surveillance has been demonstrated by detections of continued circulation after a long absence in detection of confirmed AFP cases (e.g., SOM-BAN-1 in Somalia) and of circulation before detection of confirmed AFP cases (e.g., NIE-JIS-1 in Ghana); some outbreak transmission has been detected only through environmental surveillance (e.g., NIE-SOS-6 in Nigeria).[8]

To address these challenges, GPEI adopted the 2020–2021 Strategy for the Response to Type 2 Circulating Vaccine-Derived Poliovirus as an addendum to the Polio Endgame Strategy 2019–2023.[6] The response strategy aims to improve the quality of mOPV2 SIAs through enhanced technical support, enactment of full international health emergency procedures, and enhanced population protection from paralysis through periodic intensification of routine immunization with bOPV and injectable inactivated poliovirus vaccine. After accelerated development and clinical testing of nOPV2,[9] which has a substantially lower risk for reversion to neurovirulence,[2,9] this vaccine is expected to be available in mid-2020 for initial outbreak responses under emergency use listing requirements.[10] If wider outbreak response use is allowed and ample supplies are available by the end of 2020, nOPV2 will replace Sabin mOPV2 in outbreak response to prevent new VDPV2 emergences.[6] This time line and the course of ongoing and newly emergent cVDPV outbreaks could be negatively affected during the coronavirus disease 2019 (COVID-19) pandemic because of changes in priorities for use of health care resources and decreased immunization activities. Cessation of all OPV use after certification of polio eradication will eliminate the risk of VDPV emergence.[2,4]

GPEI has offered its global technical and material assets to support the COVID-19 pandemic response and has recommended that preventive and response polio SIAs be suspended until June 1, 2020, or later. AFP and environmental surveillance activities should continue to the extent possible and according to countries' COVID-19 contexts, as well as preparations for the use of nOPV2. http://polioeradication.org/news-post/global-polio-eradication-and-covid-19/.