Serotype

Poliomyelitis eradication

Virology

Antibody

Poliovirus

Outbreak

Environmental health

Immunization

Disease Eradication

Virus

Polio vaccine

Disease

Vaccination

Polio Vaccination

Poliomyelitis

Inactivated Poliovirus Vaccine

Pathology

Pediatrics

Immunology

Medicine

MMWR Morbidity and Mortality Weekly Report

Since the Global Polio Eradication Initiative was launched in 1988 (1), the number of polio cases worldwide has declined by >99.99%. Among the three wild poliovirus (WPV) serotypes, only type 1 (WPV1) has been detected since 2012. This decline is attributable primarily to use of the live, attenuated oral poliovirus vaccine (OPV) in national routine immunization schedules and mass vaccination campaigns. The success and safety record of OPV use is offset by the rare emergence of genetically divergent vaccine-derived polioviruses (VDPVs), whose genetic drift from the parental OPV strains indicates prolonged replication or circulation (2). Circulating VDPVs (cVDPVs) can emerge in areas with low immunization coverage and can cause outbreaks of paralytic polio. In addition, immunodeficiency-associated VDPVs (iVDPVs) can emerge in persons with primary immunodeficiencies and can replicate and be excreted for years. This report presents data on VDPVs detected during January 2017-June 2018 and updates previous VDPV summaries (3). During this reporting period, new cVDPV outbreaks were detected in five countries. Fourteen newly identified persons in nine countries were found to excrete iVDPVs. Ambiguous VDPVs (aVDPVs), isolates that cannot be classified definitively, were found among immunocompetent persons and environmental samples in seven countries.

Update on Vaccine-Derived Polioviruses — Worldwide, January 2017–June 2018