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. 2021 Feb;41(2):289-302.
doi: 10.1111/risa.13485. Epub 2020 Apr 29.

Modeling Poliovirus Transmission in Borno and Yobe, Northeast Nigeria

Dominika A Kalkowska  1 , Richard Franka  2 , Jeff Higgins  3 , Stephanie D Kovacs  2 , Joseph C Forbi  2 , Steven G F Wassilak  2 , Mark A Pallansch  4 , Kimberly M Thompson  1
Affiliations

Modeling Poliovirus Transmission in Borno and Yobe, Northeast Nigeria

Dominika A Kalkowska et al. Risk Anal. 2021 Feb.

Abstract

Beginning in 2013, multiple local government areas (LGAs) in Borno and Yobe in northeast Nigeria and other parts of the Lake Chad basin experienced a violent insurgency that resulted in substantial numbers of isolated and displaced people. Northeast Nigeria represents the last known reservoir country of wild poliovirus (WPV) transmission in Africa, with detection of paralytic cases caused by serotype 1 WPV in 2016 in Borno and serotype 3 WPV in late 2012. Parts of Borno and Yobe are also problematic areas for transmission of serotype 2 circulating vaccine-derived polioviruses, and they continue to face challenges associated with conflict and inadequate health services in security-compromised areas that limit both immunization and surveillance activities. We model poliovirus transmission of all three serotypes for Borno and Yobe using a deterministic differential equation-based model that includes four subpopulations to account for limitations in access to immunization services and dynamic restrictions in population mixing. We find that accessibility issues and insufficient immunization allow for prolonged poliovirus transmission and potential undetected paralytic cases, although as of the end of 2019, including responsive program activities in the modeling suggest die out of indigenous serotypes 1 and 3 WPVs prior to 2020. Specifically, recent and current efforts to access isolated populations and provide oral poliovirus vaccine continue to reduce the risks of sustained and undetected transmission, although some uncertainty remains. Continued improvement in immunization and surveillance in the isolated subpopulations should minimize these risks. Stochastic modeling can build on this analysis to characterize the implications for undetected transmission and confidence about no circulation.

Keywords: Eradication; Nigeria; polio.

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Conflict of interest statement

Declaration of interest

None.

Figures

Figure 1.
Figure 1.
Assumed routine immunization (RI) coverage with oral poliovirus vaccine (OPV) for birth dose and one nonbirth dose, two nonbirth doses, and three or more nonbirth doses.
Figure 2.
Figure 2.. Historical supplementary immunization activities (SIAs) for Borno and Yobe by type of vaccine used and fraction of the population targeted
Abbreviations: f-PV, fractional IPV; IPV, inactivated poliovirus vaccine; bOPV, bivalent OPV; mOPV(1,2,3), monovalent OPV (serotype 1, 2, 3 containing); OPV, oral poliovirus vaccine; tOPV, trivalent OPV.
Figure 3.
Figure 3.. Reported poliovirus cases for 2001–2019, modeled paralytic incidence, and modeled detectable paralytic incidence for Borno and Yobe
Abbreviations: cVDPV2, circulating vaccine derived poliovirus serotype 2; WPV(1,3), wild poliovirus serotype 1, 3
Figure 3.
Figure 3.. Reported poliovirus cases for 2001–2019, modeled paralytic incidence, and modeled detectable paralytic incidence for Borno and Yobe
Abbreviations: cVDPV2, circulating vaccine derived poliovirus serotype 2; WPV(1,3), wild poliovirus serotype 1, 3
Figure 3.
Figure 3.. Reported poliovirus cases for 2001–2019, modeled paralytic incidence, and modeled detectable paralytic incidence for Borno and Yobe
Abbreviations: cVDPV2, circulating vaccine derived poliovirus serotype 2; WPV(1,3), wild poliovirus serotype 1, 3
See this image and copyright information in PMC

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