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. 2017 May 26;17(1):367.
doi: 10.1186/s12879-017-2443-4.

An assessment of the geographical risks of wild and vaccine-derived poliomyelitis outbreaks in Africa and Asia

Kathleen M O'Reilly  1 , Christine Lamoureux  2 , Natalie A Molodecky  3 , Hil Lyons  4 , Nicholas C Grassly  3 , Graham Tallis  2
Affiliations

An assessment of the geographical risks of wild and vaccine-derived poliomyelitis outbreaks in Africa and Asia

Kathleen M O'Reilly et al. BMC Infect Dis. .

Abstract

Background: The international spread of wild poliomyelitis outbreaks continues to threaten eradication of poliomyelitis and in 2014 a public health emergency of international concern was declared. Here we describe a risk scoring system that has been used to assess country-level risks of wild poliomyelitis outbreaks, to inform prioritisation of mass vaccination planning, and describe the change in risk from 2014 to 2016. The methods were also used to assess the risk of emergence of vaccine-derived poliomyelitis outbreaks.

Methods: Potential explanatory variables were tested against the reported outbreaks of wild poliomyelitis since 2003 using multivariable regression analysis. The regression analysis was translated to a risk score and used to classify countries as Low, Medium, Medium High and High risk, based on the predictive ability of the score.

Results: Indicators of population immunity, population displacement and diarrhoeal disease were associated with an increased risk of both wild and vaccine-derived outbreaks. High migration from countries with wild cases was associated with wild outbreaks. High birth numbers were associated with an increased risk of vaccine-derived outbreaks.

Conclusions: Use of the scoring system is a transparent and rapid approach to assess country risk of wild and vaccine-derived poliomyelitis outbreaks. Since 2008 there has been a steep reduction in the number of wild poliomyelitis outbreaks and the reduction in countries classified as High and Medium High risk has reflected this. The risk of vaccine-derived poliomyelitis outbreaks has varied geographically. These findings highlight that many countries remain susceptible to poliomyelitis outbreaks and maintenance or improvement in routine immunisation is vital.

Keywords: Migration; Outbreak; Poliomyelitis; Regression; Risk assessment; Routine immunisation; Vaccination; Vaccine-derived.

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Figures

Fig. 1
Fig. 1
Location (a) and timing (b) of wild poliomyelitis outbreaks within AFRO, EMRO, SEARO and selected EURO countries, 2003–2015. The publication of this map does not imply the expression of any opinion whatsoever on the part of WHO concerning the legal status of any territory, city, or area or of its authorities, or concerning the delimitation of its frontiers or boundaries
Fig. 2
Fig. 2
Assessed risk of wild (a, c, e, g) and vaccine-derived (b, d, f) outbreaks of poliomyelitis from January–June 2015 to July–December 2016. Confirmed outbreaks of wild and cVDPV within each time-period are also indicated and the parentheses indicate if outbreaks from previous time-periods are on-going. Nigeria was included in the wild risk assessment in January–June 2016 and was re-classified as endemic when the July–December 2016 risk assessment was made. The publication of this map does not imply the expression of any opinion whatsoever on the part of WHO concerning the legal status of any territory, city, or area or of its authorities, or concerning the delimitation of its frontiers or boundaries
Fig. 3
Fig. 3
Location (a) and timing (b) of vaccine-derived poliomyelitis outbreaks within the AFRO, EMRO, SEARO and selected EURO countries, 2003–2016. The publication of this map does not imply the expression of any opinion whatsoever on the part of WHO concerning the legal status of any territory, city, or area or of its authorities, or concerning the delimitation of its frontiers or boundaries
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