Vaccine-Derived Polioviruses (VDPVs) are strains of the poliovirus that have genetically mutated from the strain contained in the oral poliovirus vaccine (OPV). While the OPV is highly effective in immunizing individuals and eradicating polio, under rare circumstances, the attenuated virus used in the vaccine can change over time and behave more like the wild poliovirus. These mutated strains are known as VDPVs and can cause outbreaks in populations with low immunization coverage.
