What is a circulating vaccine-derived poliovirus (cVDPV)?

• A. A poliovirus that originates from OPV and circulates within under-immunized populations
• B. A wild poliovirus strain found only in natural settings
• C. A synthetic virus unrelated to poliovirus
• D. A non-polio enterovirus

Answer: (A)

A circulating vaccine-derived poliovirus is the weakened virus from the oral polio vaccine that has mutated and begun to circulate in a population with insufficient immunity, potentially causing poliomyelitis. It originates from the live vaccine strain, not from a naturally occurring wild poliovirus, and it becomes a problem only when the attenuated virus spreads in under-immunized communities and accumulates mutations that restore neurovirulence. This is distinct from a wild poliovirus and from non-polio enteroviruses, and it explains why high vaccination coverage is crucial—to stop transmission and prevent the vaccine strain from circulating and reverting.