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Abstract Background Immunodeficient persons with persistent vaccine-related poliovirus infection may serve as a potential reservoir for reintroduction of polioviruses after wild poliovirus eradication, posing a risk of their further circulation in inadequately immunized populations. Methods To estimate the potential for vaccine-related poliovirus persistence among HIV-infected persons, we studied poliovirus excretion following vaccination among children at an orphanage in Kenya. For 12 months after national immunization days, we collected serial stool specimens from orphanage residents aged Results Twenty-four children (15 HIV-infected, 9 HIV-uninfected) were enrolled, and 255 specimens (170 from HIV-infected, 85 from HIV-uninfected) were collected. All HIV-infected children had mildly or moderately symptomatic HIV-disease and moderate-to-severe immunosuppression. Fifteen participants shed vaccine-related polioviruses, and 22 shed NPEV at some point during the study period. Of 46 poliovirus-positive specimens, 31 were from HIV-infected, and 15 from HIV-uninfected children. No participant shed polioviruses for ≥ 6 months. Genomic sequencing of poliovirus isolates did not reveal any genetic evidence of long-term shedding. There was no long-term shedding of NPEV. Conclusion The results indicate that mildly to moderately symptomatic HIV-infected children retain the ability to clear enteroviruses, including vaccine-related poliovirus. Larger studies are needed to confirm and generalize these findings.

Delays in achieving the global eradication of wild poliovirus transmission continue to postpone subsequent cessation of all oral poliovirus vaccine (OPV) use. Countries must stop OPV use to end all cases of poliomyelitis, including vaccine‐associated paralytic polio (VAPP) and cases caused by vaccine‐derived polioviruses (VDPVs). The Global Polio Eradication Initiative (GPEI) coordinated global cessation of all type 2 OPV (OPV2) use in routine immunization in 2016 but did not successfully end the transmission of type 2 VDPVs (VDPV2s), and consequently continues to use type 2 OPV (OPV2) for outbreak response activities. Using an updated global poliovirus transmission and OPV evolution model, we characterize outbreak response options for 2019–2029 related to responding to VDPV2 outbreaks with a genetically stabilized novel OPV (nOPV2) strain or with the currently licensed monovalent OPV2 (mOPV2). Given uncertainties about the properties of nOPV2, we model different assumptions that appear consistent with the evidence on nOPV2 to date. Using nOPV2 to respond to detected cases may reduce the expected VDPV and VAPP cases and the risk of needing to restart OPV2 use in routine immunization compared to mOPV2 use for outbreak response. The actual properties, availability, and use of nOPV2 will determine its effects on type 2 poliovirus transmission in populations. Even with optimal nOPV2 performance, countries and the GPEI would still likely need to restart OPV2 use in routine immunization in OPV‐using countries if operational improvements in outbreak response to stop the transmission of cVDPV2s are not implemented effectively. [ABSTRACT FROM AUTHOR]

After the globally coordinated cessation of any serotype of oral poliovirus vaccine (OPV), some risks remain from undetected, existing homotypic OPV‐related transmission and/or restarting transmission due to several possible reintroduction risks. The Global Polio Eradication Initiative (GPEI) coordinated global cessation of serotype 2‐containing OPV (OPV2) in 2016. Following OPV2 cessation, the GPEI and countries implemented activities to withdraw all the remaining trivalent OPV, which contains all three poliovirus serotypes (i.e., 1, 2, and 3), from the supply chain and replace it with bivalent OPV (containing only serotypes 1 and 3). However, as of early 2020, monovalent OPV2 use for outbreak response continues in many countries. In addition, outbreaks observed in 2019 demonstrated evidence of different types of risks than previously modeled. We briefly review the 2019 epidemiological experience with serotype 2 live poliovirus outbreaks and propose a new risk for unexpected OPV introduction for inclusion in global modeling of OPV cessation. Using an updated model of global poliovirus transmission and OPV evolution with and without consideration of this new risk, we explore the implications of the current global situation with respect to the likely need to restart preventive use of OPV2 in OPV‐using countries. Simulation results without this new risk suggest OPV2 restart will likely need to occur (81% of 100 iterations) to manage the polio endgame based on the GPEI performance to date with existing vaccine tools, and with the new risk of unexpected OPV introduction the expected OPV2 restart probability increases to 89%. Contingency planning requires new OPV2 bulk production, including genetically stabilized OPV2 strains. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Nearly 20 years after the year 2000 target for global wild poliovirus (WPV) eradication, live polioviruses continue to circulate with all three serotypes posing challenges for the polio endgame. We updated a global differential equation‐based poliovirus transmission and stochastic risk model to include programmatic and epidemiological experience through January 2020. We used the model to explore the likely dynamics of poliovirus transmission for 2019–2023, which coincides with a new Global Polio Eradication Initiative Strategic Plan. The model stratifies the global population into 72 blocks, each containing 10 subpopulations of approximately 10.7 million people. Exported viruses go into subpopulations within the same block and within groups of blocks that represent large preferentially mixing geographical areas (e.g., continents). We assign representative World Bank income levels to the blocks along with polio immunization and transmission assumptions, which capture some of the heterogeneity across countries while still focusing on global poliovirus transmission dynamics. We also updated estimates of reintroduction risks using available evidence. The updated model characterizes transmission dynamics and resulting polio cases consistent with the evidence through 2019. Based on recent epidemiological experience and prospective immunization assumptions for the 2019–2023 Strategic Plan, the updated model does not show successful eradication of serotype 1 WPV by 2023 or successful cessation of oral poliovirus vaccine serotype 2‐related viruses. [ABSTRACT FROM AUTHOR]

Poliovirus-positive sewage samples are characterized by using a new protocol for virus concentration and either RD or L20B cells for primary virus isolation. The studies have shown continuous introduction of Sabin-like polioviruses into the community, but high hygienic standards might prevent the more efficient fecal-oral transmission and prevent only the less efficient oral-oral transmission.

Since most poliovirus infections occur with no paralytic symptoms, the possibility of silent circulation complicates the confirmation of the end of poliovirus transmission. Based on empirical field experience and theoretical modeling results, the Global Polio Eradication Initiative identified three years without observing paralytic cases from wild polioviruses with good acute flaccid paralysis surveillance as an indication of sufficient confidence that poliovirus circulation stopped. The complexities of real populations and the imperfect nature of real surveillance systems subsequently demonstrated the importance of specific modeling for areas at high risk of undetected circulation, resulting in varying periods of time required to obtain the same level of confidence about no undetected circulation. Using a poliovirus transmission model that accounts for variability in transmissibility and neurovirulence for different poliovirus serotypes and characterizes country‐specific factors (e.g., vaccination and surveillance activities, demographics) related to wild and vaccine‐derived poliovirus transmission in Pakistan and Afghanistan, we consider the probability of undetected poliovirus circulation for those countries once apparent die‐out occurs (i.e., in the absence of any epidemiological signals). We find that gaps in poliovirus surveillance or reaching elimination with borderline sufficient population immunity could significantly increase the time to reach high confidence about interruption of live poliovirus transmission, such that the path taken to achieve and maintain poliovirus elimination matters. Pakistan and Afghanistan will need to sustain high‐quality surveillance for polioviruses after apparent interruption of transmission and recognize that as efforts to identify cases or circulating live polioviruses decrease, the risks of undetected circulation increase and significantly delay the global polio endgame. [ABSTRACT FROM AUTHOR]

Objective To characterise the costs, including for environmental surveillance (ES), of the Global Polio Laboratory Network (GPLN) that provides laboratory support to the Global Polio Eradication Initiative (GPEI). Design and participants We conducted a survey of the network across 92 countries of the 146 GPLN laboratories plus three non-GPLN laboratories that concentrate environmental samples to collect information about their activities, characteristics and costs during 2016. We estimate the total costs using regression of reported responses and complementing the findings with GPEI data. Results We received responses from 132 (89%) of the 149 laboratories, with variable response rates for individual questions. We estimate that processing samples of patients with acute flaccid paralysis leads to total costs of approximately $28 million per year (2016 US$) based on extrapolation from reported costs of $16 million, of which 61% were supported by internal (national) funds. Fifty-nine (45%) of the 132 responding laboratories reported supporting ES and we estimate an additional $5.3 million of recurring costs for ES activities performed by the laboratories. The reported costs do not include an estimated additional $10 million of annual global and regional costs to coordinate and support the GPLN. On average, the staff supported by funding for polio in the responding laboratories spent 30% of their time on nonpolio activities. We estimate total costs for laboratory support of approximately $43 million (note that this estimate does not include any field or other non-laboratory costs of polio surveillance). Conclusions Although countries contribute significantly to the GPLN financing, many laboratories currently depend on GPEI funds, and these laboratories also support the laboratory component of surveillance activities for other diseases. Sustaining critical global surveillance for polioviruses and transitioning support for other disease programmes will require continued significant funding after polio certification. [ABSTRACT FROM AUTHOR]

In 1998, an outbreak of enterovirus 71-associated hand, foot, and mouth disease occurred in Taiwan. Pathologic studies of two fatal cases with similar clinical features revealed two different causative agents, [...]

Polio An American Story by David M. Oshinsky Oxford University Press, New York, 2005. 340 pp. $30, 18.99 £. ISBN 0-19515294-8. Splendid Solution Jonas Salk and the Conquest of Polio [...]

The Global Polio Laboratory Network (GPLN) began building in the late 1980s on a 3-tiered structure of 146 laboratories with different and complementary technical and support capacities (poliovirus isolation, molecular strain characterization including sequencing, quality assurance, and research). The purpose of this network is to provide timely and accurate laboratory results to the Global Polio Eradication Initiative. Deeply integrated with field case-based surveillance, it ultimately provides molecular epidemiological data from polioviruses used to inform programmatic and immunization activities. This network of global coverage requires substantial investments in laboratory infrastructure, equipment, supplies, reagents, quality assurance, staffing and training, often in resource-limited settings. The GPLN has not only developed country capacities, but it also serves as a model to other global laboratory networks for vaccine-preventable diseases that will endure after the polio eradication goal is achieved. Leveraging lessons learned during past 27 years, the authors discuss options for transitioning GPLN assets to support control of other viral vaccine-preventable, emerging, and reemerging diseases. [ABSTRACT FROM AUTHOR]