Identifying Reinfected Subnational Areas in Chronic Type 2 Polio Outbreaks, 2016–2025
- Presentation Day/Time: Wednesday, April 22, 10:05 AM
- Presenter: Avnika Amin, PhD, MSPH, National Center for Immunization and Respiratory Diseases, Division of Bacterial Diseases
The Issue
- Since the removal of type 2 oral poliovirus vaccine (OPV2) from routine immunization in 2016, 62 countries have experienced detections of circulating vaccine-derived poliovirus, type 2 (cVDPV2), with some detecting the virus for years despite vaccination campaigns to interrupt transmission.
What We Did
- We assessed surveillance data from cVDPV2 outbreaks to identify factors that may facilitate persistent circulation and inform outbreak response practices.
What We Found
- We found that chronic cVDPV2 outbreaks that lasted more than a year impact a large proportion of provinces, regions, or states within affected countries more frequently than outbreaks that ended within a year. Reinfection (detecting the virus again after more than a year of no detections) of provinces, regions, or states is common during chronic outbreaks.
What This Means
- In the absence of routine OPV2 immunization, countries with chronic outbreaks could benefit from OPV2 campaigns with larger scope covering areas surrounding transmission zones to achieve sufficient population immunity to interrupt cVDPV2 transmission.
