Estimated Effect of Inactivated Poliovirus Vaccine Campaigns, Nigeria and Pakistan, January 2014–April 2016

Shirreff, George; Wadood, Mufti Zubair; Vaz, Rui G.; Sutter, Roland W.; Grassly, Nicholas C

doi:10.3201/eid2302.161210

Cited by 16 publications

(16 citation statements)

References 18 publications

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“…In agreement with reported mixed evidence about the benefit of past IPV use in endemic areas, this study finds a moderate effect of IPV use to date in Pakistan and Afghanistan on population immunity to WPV1 or cVDPV2 transmission compared to reliance on OPV‐only through 2017. The benefit comes primarily from the assumed effect of IPV boosting on intestinal immunity observed in clinical trials but further traces to our assumption that oropharyngeal transmission plays some role in overall poliovirus transmission and that IPV‐only can effectively limit oropharyngeal transmission .…”

Section: Discussionsupporting

confidence: 90%

“…However, supply limitations forced the GPEI to delay IPV introduction in 20 countries and caused stock‐outs in other countries . Nevertheless, the GPEI prioritized IPV use in supplemental immunization activities (SIAs, i.e., campaigns that target children within a broad age range, typically through age four years, regardless of immunization history) based on evidence that IPV boosts the intestinal immunity of individuals with immunity from prior LPV (i.e., WPV, OPV, OPV‐related, and VDPV) infections, although modeling provided mixed evidence that this translates into a significant effect on transmission at the population level …”

Section: Introductionmentioning

confidence: 99%

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

Tebbens¹,

Pallansch

Cochi

et al. 2018

Risk Analysis

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Due to security, access, and programmatic challenges in areas of Pakistan and Afghanistan, both countries continue to sustain indigenous wild poliovirus (WPV) transmission and threaten the success of global polio eradication and oral poliovirus vaccine (OPV) cessation. We fitted an existing differential-equation-based poliovirus transmission and OPV evolution model to Pakistan and Afghanistan using four subpopulations to characterize the well-vaccinated and undervaccinated subpopulations in each country. We explored retrospective and prospective scenarios for using inactivated poliovirus vaccine (IPV) in routine immunization or supplemental immunization activities (SIAs). The undervaccinated subpopulations sustain the circulation of serotype 1 WPV and serotype 2 circulating vaccine-derived poliovirus. We find a moderate impact of past IPV use on polio incidence and population immunity to transmission mainly due to (1) the boosting effect of IPV for individuals with preexisting immunity from a live poliovirus infection and (2) the effect of IPV-only on oropharyngeal transmission for individuals without preexisting immunity from a live poliovirus infection. Future IPV use may similarly yield moderate benefits, particularly if access to undervaccinated subpopulations dramatically improves. However, OPV provides a much greater impact on transmission and the incremental benefit of IPV in addition to OPV remains limited. This study suggests that despite the moderate effect of using IPV in SIAs, using OPV in SIAs remains the most effective means to stop transmission, while limited IPV resources should prioritize IPV use in routine immunization.

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Section: Discussionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

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

Tebbens¹,

Pallansch

Cochi

et al. 2018

Risk Analysis

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“…iii. The issue of cVDPV (Circulating Vaccine Derived Polio Virus) should be effectively tackled as this poses significant risk to the successful elimination of the virus [35,36]. The synchronization of withdrawal of oral polio vaccine and the subsequent introduction of inactivated polio vaccine is pivotal to achieving this aim [37].…”

Section: Recommendations and Possible Way Outmentioning

confidence: 99%

Current Status and Underlying Problems of Eradication of Poliomyelitis in the Remaining Endemic Countries

Ike¹,

Reward²,

Mbaawuaga³

et al. 2018

EJPM

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In 1988, the World Health Assembly of the World Health Organization (WHO) launched the Global Polio Eradication Initiative (GPEI), with the resolve to interrupt transmission of wild poliovirus (WPV) worldwide by the year 2000.Eighteen years after the intended year of eradication, that target is yet to be achieved. To investigate the reasons behind this, a check of recent publications on poliomyelitis and polio virus was carried out. The databases and websites of institutions and organizations involved in the polio eradication programme were also checked. The findings showed that although the goal of interrupting polio transmission has not been meet, a lot of progress has been made. By 2006, transmission of WPV had been interrupted in all but four countries: Afghanistan, India, Nigeria and Pakistan. In February 2012, India was delisted from the list of polio-endemic countries leaving the remaining 3 countries as the only endemic countries in the world. Wild type 2 and 3 viruses have both been eliminated from circulations. The number of polio cases in the remaining endemic countries has reduced drastically. Nigeria is close to the target, but is yet to be certified polio-free, having experienced a setback in 2016. However, as long as transmission of WPV continues in these countries, the world cannot be free from the disease, as these countries serve as reservoirs of infection and sources of export of the virus to other countries. To be able to achieve the target of interrupting the transmission of WPV in the remaining endemic countries, the identified problems, particularly conflict in the countries concerned, will have to be factored into the programmes geared toward eradication of the disease.

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“…Various mathematical and statistical models studied the poliovirus situation in Pakistan and Afghanistan to inform strategies to finish eradication in the two countries (Duintjer Tebbens et al., ; Mercer et al., ; Molodecky et al., ; Shirreff, Wadood, Vaz, Sutter, & Grassly, ). Immunization plans available as of late 2017 suggest no increase in the frequency of supplemental immunization activities (SIAs) in 2018 and 2019 compared to prior years, which implies insufficient intensity of efforts to interrupt WPV1 transmission unless the quality of activities substantially improves (Duintjer Tebbens et al., ; Kalkowska, Duintjer Tebbens, Pallansch, & Thompson, ).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Proactive and Reactive Strategies for Polio Eradication Activities in Pakistan and Afghanistan

Tebbens¹,

Thompson²

2018

Risk Analysis

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Only Pakistan and Afghanistan reported any polio cases caused by serotype 1 wild polioviruses (WPV1s) in 2017. With the dwindling cases in both countries and pressure to finish eradication with the least possible resources, a danger exists of inappropriate prioritization of efforts between the two countries and insufficient investment in the two countries to finish the job. We used an existing differential‐equation‐based poliovirus transmission and oral poliovirus (OPV) evolution model to simulate a proactive strategy to stop transmission, and different hypothetical reactive strategies that adapt the quality of supplemental immunization activities (SIAs) in response to observed polio cases in Pakistan and Afghanistan. To account for the delay in perception and adaptation, we related the coverage of the SIAs in high‐risk, undervaccinated subpopulations to the perceived (i.e., smoothed) polio incidence. Continuation of the current frequency and quality of SIAs remains insufficient to eradicate WPV1 in Pakistan and Afghanistan. Proactive strategies that significantly improve and sustain SIA quality lead to WPV1 eradication and the prevention of circulating vaccine‐derived poliovirus (cVDPV) outbreaks. Reactive vaccination efforts that adapt moderately quickly and independently to changes in polio incidence in each country may succeed in WPV1 interruption after several cycles of outbreaks, or may interrupt WPV1 transmission in one country but subsequently import WPV1 from the other country or enable the emergence of cVDPV outbreaks. Reactive vaccination efforts that adapt independently and either more rapidly or more slowly to changes in polio incidence in each country may similarly fail to interrupt WPV1 transmission and result in oscillations of the incidence. Reactive strategies that divert resources to the country of highest priority may lead to alternating large outbreaks. Achieving WPV1 eradication and subsequent successful OPV cessation in Pakistan and Afghanistan requires proactive and sustained efforts to improve vaccination intensity in under‐vaccinated subpopulations while maintaining high population immunity elsewhere.

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Estimated Effect of Inactivated Poliovirus Vaccine Campaigns, Nigeria and Pakistan, January 2014–April 2016

Cited by 16 publications

References 18 publications

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

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

Current Status and Underlying Problems of Eradication of Poliomyelitis in the Remaining Endemic Countries

Evaluation of Proactive and Reactive Strategies for Polio Eradication Activities in Pakistan and Afghanistan

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