Detection and Initial Response to a Type 2 Vaccine-Derived Poliovirus - Sichuan Province, China, 2019

After the type 2 strain of the live, attenuated poliovirus vaccine was withdrawn globally in 2016, any identification of a type 2 poliovirus is a Public Health Emergency of International Concern. A vaccine-derived type 2 poliovirus (VDPV2) was identified in Sichuan, prompting an urgent, comprehensive investigation and response.

Type 2 monovalent, live, attenuated oral poliovirus vaccine (mOPV2) is being used to respond to the numerous VDPV2 outbreaks seen around the world. In contrast, the response in Sichuan used Sabin strain inactivated poliovirus (sIPV) to stop circulation of the VDPV2. In the 6 months following the vaccination response, there have been no VDPV2s detected in Sichuan, despite extensive search.

Further search for the VDPV2 must continue in order to determine whether transmission has been stopped. The ongoing investigation and response to the Sichuan VDPV2 is providing evidence to the Global Polio Eradication Initiative on managing VDPV2 outbreaks.