This March 2022 WHO publication is the fourth version of the GPEI Standard Operating Procedures (SOP) for responding to a poliovirus event or outbreak. Available in English, French, Arabic, Spanish, and Portuguese, it constitutes the definitive operational framework for detection, investigation, assessment, and vaccination response to any poliovirus detection: wild poliovirus (WPV), circulating vaccine-derived poliovirus (cVDPV), or ambiguous events. Version 4 incorporates lessons from expanded cVDPV2 outbreak experience of 2017–2021 and the introduction of nOPV2 as the primary vaccine for cVDPV2 response.

The SOPs open with a decision framework for classifying a poliovirus detection event and determining appropriate response scale based on virus type, population immunity context, surveillance history, and spread risk.

Core content covers sequential response steps: initial assessment, outbreak response assessment (OBR/OBRA), first SIA, subsequent response rounds, surveillance intensification, and outbreak closure. For each step, the SOPs specify minimum response requirements, responsible actors, timelines from event detection, and quality standards against which response performance will be evaluated. Particular detail is provided for the critical first 72 hours — the window during which rapid case investigation, specimen collection, and initial planning must occur.

Specific SOPs address wild poliovirus (including importation events into previously polio-free areas) and cVDPV2, where vaccine choice (nOPV2 vs. mOPV2) and geographic response scope require specific decision guidance. Environmental surveillance activation protocols and the OBRA tool are integrated into the framework. Response closure criteria specify the conditions required for declaring an outbreak closed.

Every cVDPV2 and WPV1 response worldwide is expected to follow these SOPs. Non-adherence is a primary risk factor for outbreak response failure.

Who should read this: Outbreak response coordinators, national immunization program managers, GPEI partner organization emergency response teams, WHO country and regional office staff, district health officials, surveillance officers, laboratory directors, SIA coordinators, logistics managers.

Document value: Definitive operational guide for all poliovirus outbreak response activities. Every cVDPV2 and WPV1 response worldwide is expected to follow these SOPs. Adherence is tracked by the IMB.

Available in: English, French, Arabic, Spanish, Portuguese