Global Circulating Vaccine-derived Poliovirus (cVDPV) as of 18 July 2023

cVDPV2 is a circulating vaccine-derived poliovirus. It is a form of polio that can spread within communities due to low immunization rates. cVDPV2 is the most prevalent type of cVDPV, with 959 cases occurring globally in 2020. The original “wild” poliovirus (WPV) and the much more common modified oral vaccination strains are the two causes of recent polio infections. The three wild polio strains each gave rise to different cVDPV strains, with cVDPV2 being the most prevalent.

If a population is seriously under-immunized, there are enough susceptible children for the excreted vaccinederived polioviruses to begin circulating in the community. If the vaccine-virus is able to circulate for a prolonged period of time uninterrupted, it can mutate and, over the course of 12-18 months, reacquire neurovirulence. These viruses are called circulating vaccine-derived polioviruses (cVDPV).

The lower the population immunity, the longer these viruses survive. The longer they survive, the more they replicate, change, and exchange genetic material with other enteroviruses as they spread through a community. If a population is fully immunized against polio, it will be protected against the spread of both wild and vaccine strains of poliovirus.

Episodes of circulating vaccine-derived poliovirus are rare. Over the past ten years a period during which more than 10 billion doses of oral polio vaccine were given worldwide – cVDPV outbreaks resulted in fewer than 800 cases. In the same period, in the absence of vaccination with OPV, more than 6.5 million children would have been paralysed by wild poliovirus.