cVDPV

Circulating vaccine-derived poliovirus (cVDPV) is a poliovirus that originated from the attenuated virus used in the oral polio vaccine (OPV) and has mutated to regain properties that allow it to spread in a population. VDPVs are categorized as circulating when they evidence sustained person-to-person transmission in communities, typically causing outbreaks similar to those caused by wild poliovirus.

cVDPV arises when vaccine-derived strains circulate in populations with low vaccination coverage and poor sanitation. As the Sabin strain replicates in the gut, it can accumulate mutations; once it diverges sufficiently from the original vaccine strain, it can regain neurovirulence and transmissibility. The risk is highest in areas with gaps in routine immunization, where fecal-oral transmission is more likely.

There are three genetic types of cVDPV: cVDPV1, cVDPV2, and cVDPV3, corresponding to the Sabin type they originated from. Diagnosis relies on laboratory analysis of poliovirus isolates and genetic sequencing to measure divergence from the corresponding vaccine strain. Surveillance combines acute flaccid paralysis (AFP) reporting and environmental surveillance of sewage to detect circulating strains.

Control and prevention focus on rapid outbreak response and increasing population immunity. This includes strengthening routine immunization with the polio vaccines and conducting targeted immunization campaigns, sometimes using OPV for mucosal immunity, or switching vaccines to reduce risk of specific serotypes. Global eradication efforts emphasize ending OPV use after wild poliovirus eradication while maintaining high immunity levels to prevent cVDPV emergence and transmission.