N. Engl. J. Med. 379, 834–845 (2018).

Following synchronized global withdrawal of the oral poliovirus vaccine type 2 (OPV2), outbreaks of vaccine-derived poliovirus (VDPV) type 2 occur in populations at high risk.

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Laguna Design/Science Source

To ensure the full elimination of poliovirus, OPV must be withdrawn to prevent outbreaks of VDPV. This was synchronously begun worldwide in April 2016 with OPV2.

By analyzing stool samples from the populace of some countries in addition to sewage samples taken from several of these countries, researchers were able to trace the success of OPV elimination in 118 countries in total. While the rate of detection of vaccine virus declined overall, nine VDPV2 outbreaks were reported in areas associated with low coverage of immunization and low levels of population immunity. Prevention of further outbreaks in these areas is a priority.