Combinations of Quality and Frequency of Immunization Activities to Stop and Prevent Poliovirus Transmission in the High-Risk Area of Northwest Nigeria

Abstract

BackgroundFrequent supplemental immunization activities (SIAs) with the oral poliovirus vaccine (OPV) represent the primary strategy to interrupt poliovirus transmission in the last endemic areas.Materials and MethodsUsing a differential-equation based poliovirus transmission model tailored to high-risk areas in Nigeria, we perform one-way and multi-way sensitivity analyses to demonstrate the impact of different assumptions about routine immunization (RI) and the frequency and quality of SIAs on population immunity to transmission and persistence or emergence of circulating vaccine-derived polioviruses (cVDPVs) after OPV cessation.ResultsMore trivalent OPV use remains critical to avoid serotype 2 cVDPVs. RI schedules with or without inactivated polio vaccine (IPV) could significantly improve population immunity if coverage increases well above current levels in under-vaccinated subpopulations. Similarly, the impact of SIAs on overall population immunity and cVDPV risks depends on their ability to reach under-vaccinated groups (i.e., SIA quality). Lower SIA coverage in the under-vaccinated subpopulation results in a higher frequency of SIAs needed to maintain high enough population immunity to avoid cVDPVs after OPV cessation.ConclusionsNational immunization program managers in northwest Nigeria should recognize the benefits of increasing RI and SIA quality. Sufficiently improving RI coverage and improving SIA quality will reduce the frequency of SIAs required to stop and prevent future poliovirus transmission. Better information about the incremental costs to identify and reach under-vaccinated children would help determine the optimal balance between spending to increase SIA and RI quality and spending to increase SIA frequency.

Modeling Poliovirus Transmission in Pakistan and Afghanistan to Inform Vaccination Strategies in Undervaccinated Subpopulations

“…WPV elimination in northern India ultimately succeeded when vaccination efforts reached previously unidentified missed children. Similarly, interruption of WPVs and cVDPV2s in northwest Nigeria required intense efforts to identify missed communities . However, insufficient tOPV intensification before the switch allowed the emergence of a new cVDPV2 in Pakistan, and prolonged access challenges in Borno in northeast Nigeria allowed cVDPV2 transmission to persist through the switch .…”

“…The geographic area of Pakistan and Afghanistan represents the only epidemiological region besides the Lake Chad Basin in which WPV1 eradication and post‐switch risk management represent simultaneous critical priorities. We previously developed a deterministic, differential‐equation‐based model of poliovirus transmission and OPV evolution (i.e., the DEB model) that we tailored to settings like northwest Nigeria and northern India to help inform polio endgame strategies . We use the DEB model to reproduce the epidemiological evidence related to poliovirus transmission in Pakistan and Afghanistan, characterize population immunity to poliovirus transmission of all three serotypes, and explore IPV strategies aimed at WPV1 eradication and serotype 2 risk management.…”

Using integrated modeling to support the global eradication of vaccine‐preventable diseases

“…• What are the impacts of various immunization options on poliovirus transmission and population immunity to poliovirus transmission in various settings of interest (Thompson et al ., , ; Kalkowska et al ., , , ; Duintjer Tebbens et al ., ; Thompson and Duintjer Tebbens, , ; Duintjer Tebbens and Thompson, )?…”

“…variability within stocks) and uncertainty about these averages. We used deterministic DEB models of poliovirus transmission (Duintjer Tebbens et al ., , ) to derive many important policy insights, including the critical importance of responding rapidly to outbreaks, even at the expense of initially lower coverage (World Health Organization, ; Thompson et al ., ), the counter‐intuitive need to intensify OPV use prior to its cessation as opposed to a gradual phase‐out (Duintjer Tebbens and Thompson, ; Kalkowska et al ., , ; Thompson and Duintjer Tebbens, ), the need to synchronize OPV cessation and verify the complete withdrawal of OPV (Duintjer Tebbens et al ., , , ), and numerous insights related to different OPV and IPV vaccination strategies to achieve and maintain eradication in specific settings (Thompson et al ., , ; Duintjer Tebbens et al ., , ; Kalkowska et al ., , , ; Thompson and Duintjer Tebbens, , ).…”

Costs and Benefits of Including Inactivated in Addition to Oral Poliovirus Vaccine in Outbreak Response After Cessation of Oral Poliovirus Vaccine Use

“…Using a previously developed model of poliovirus transmission and OPV evolution, 2,40–44 this study examines the potential costs and benefits of adding IPV to oSIA in response to a hypothetical possible outbreak after OPV2 cessation in northwest Nigeria.…”