Via MMWR, a long report: Continued Endemic Wild Poliovirus Transmission in Security-Compromised Areas — Nigeria, 2016. Excerpt from the discussion:
The recent finding of prolonged undetected WPV circulation in Borno State highlights key challenges facing polio eradication efforts in Nigeria and globally. Although the large-scale outbreak response SIA and surveillance activities conducted in the Lake Chad basin region were considered successful, conflict-related inaccessibility might continue to limit surveillance and immunization activities, raising concerns about further undetected WPV and cVDPV transmission.
To reduce the potential for persistent virus transmission, it is important to increase polio surveillance quality and vaccination coverage among cohorts of persons in unimmunized and underimmunized populations, prioritizing persons living in recently accessible areas, IDP camps, and refugee communities.
As has been observed in Afghanistan and Pakistan, the two other countries that have not yet interrupted endemic WPV transmission, insurgency-related insecurity can restrict access to populations in conflict settings, potentially imposing limits on implementation of polio eradication activities, including high-quality immunization and surveillance activities (9,10).
In Borno State, the restriction of the implementation of polio eradication activities in insurgent-held areas has been absolute: no polio eradication activities occurred in those areas. Despite multiple SIA rounds conducted in accessible areas of Borno State prior to August 2016 for which all children were eligible, two of the four children with WPV had never received polio vaccine, and the other two did not complete the polio vaccination series.
This finding validates longstanding concerns about WPV circulation among populations that have become susceptible because of the inability to reach and fully vaccinate children in security-compromised areas. Although recent gains made by the Nigerian military have led to an increase in the number of areas now accessible to polio eradication activities, approximately 40% of settlement communities in Borno State are still classified as fully inaccessible.
Unless a substantial proportion of children in these settlement communities are reached and vaccinated, it will be difficult to interrupt WPV transmission in the inaccessible areas of Borno State.