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Background: Prior to measles vaccine introduction in 1963, measles virus caused hundreds of thousands of annual reported cases, which led to substantial US morbidity, mortality, and costs. Similarly, congenital rubella syndrome (CRS) led to highly visible and tragic lifelong disability for thousands of Americans, before rubella vaccine introduction in 1969. The US certified national virus transmission elimination of indigenous measles in 2000 and rubella in 2004. Methods: Applying an existing integrated transmission and economic model, this analysis characterizes the net benefits of US investments in measles (1963–2030) and rubella (1969–2030) immunization assuming continued high routine immunization coverage. Due to importation risks, the US maintains two doses of both vaccines in its routine immunization schedule. Results: This analysis estimates total US costs of 8.1 billion (economics reported in 2023 US dollars) for measles immunization for 1963–2023 and 14.1 billion for rubella immunization for 1969–2023. The analysis estimates an additional approximately 1.2 billion for measles immunization and 1.5 billion for rubella immunization expected for 2024–2030. Historical and future US investments prevented an estimated approximately 237 million measles infections, 228,000 measles deaths, 193 million rubella infections, and 166,000 CRS cases. These investments imply net benefits (from avoided treatment costs minus immunization costs) of approximately 310 billion for measles and 430 billion for rubella and CRS, even without incorporating avoided productivity losses and intangible costs. Conclusions: US investments in measles and rubella immunization continue to provide enormous savings of human and financial costs and to prevent substantial mortality and morbidity. [ABSTRACT FROM AUTHOR]

In 2022, global poliovirus modeling suggested that coordinated cessation of bivalent oral poliovirus vaccine (bOPV, containing Sabin-strain types 1 and 3) in 2027 would likely increase the risks of outbreaks and expected paralytic cases caused by circulating vaccine-derived polioviruses (cVDPVs), particularly type 1. The analysis did not include the implementation of planned, preventive supplemental immunization activities (pSIAs) with bOPV to achieve and maintain higher population immunity for types 1 and 3 prior to bOPV cessation. We reviewed prior published OPV cessation modeling studies to support bOPV cessation planning. We applied an integrated global poliovirus transmission and OPV evolution model after updating assumptions to reflect the epidemiology, immunization, and polio eradication plans through the end of 2023. We explored the effects of bOPV cessation in 2027 with and without additional bOPV pSIAs prior to 2027. Increasing population immunity for types 1 and 3 with bOPV pSIAs (i.e., intensification) could substantially reduce the expected global risks of experiencing cVDPV outbreaks and the number of expected polio cases both before and after bOPV cessation. We identified the need for substantial increases in overall bOPV coverage prior to bOPV cessation to achieve a high probability of successful bOPV cessation. [ABSTRACT FROM AUTHOR]

In 2010, an expert advisory panel convened by the World Health Organization to assess the feasibility of measles eradication concluded that (1) measles can and should be eradicated, (2) eradication by 2020 is feasible if measurable progress is made toward existing 2015 measles mortality reduction targets, (3) measles eradication activities should occur in the context of strengthening routine immunization services, and (4) measles eradication activities should be used to accelerate control and elimination of rubella and congenital rubella syndrome (CRS). The expert advisory panel also emphasized the critical role of research and innovation in any disease control or eradication program. In May 2011, a meeting was held to identify and prioritize research priorities to support measles and rubella/CRS control and potential eradication activities. This summary presents the questions identified by the meeting participants and their relative priority within the following categories: (1) measles epidemiology, (2) vaccine development and alternative vaccine delivery, (3) surveillance and laboratory methods, (4) immunization strategies, (5) mathematical modeling and economic analyses, and (6) rubella/CRS control and elimination.

Background In July 2022, New York State (NYS) reported a case of paralytic polio in an unvaccinated young adult, and subsequent wastewater surveillance confirmed sustained local transmission of type 2 vaccine-derived poliovirus (VDPV2) in NYS with genetic linkage to the paralyzed patient. Methods We adapted an established poliovirus transmission and oral poliovirus vaccine evolution model to characterize dynamics of poliovirus transmission in NYS, including consideration of the immunization activities performed as part of the declared state of emergency. Results Despite sustained transmission of imported VDPV2 in NYS involving potentially thousands of individuals (depending on seasonality, population structure, and mixing assumptions) in 2022, the expected number of additional paralytic cases in years 2023 and beyond is small (less than 0.5). However, continued transmission and/or reintroduction of poliovirus into NYS and other populations remains a possible risk in communities that do not achieve and maintain high immunization coverage. Conclusions In countries such as the United States that use only inactivated poliovirus vaccine, even with high average immunization coverage, imported polioviruses may circulate and pose a small but nonzero risk of causing paralysis in nonimmune individuals. [ABSTRACT FROM AUTHOR]

In May 2016, the Global Polio Eradication Initiative (GPEI) coordinated the cessation of all use of type 2 oral poliovirus vaccine (OPV2), except for emergency outbreak response. Since then, paralytic polio cases caused by type 2 vaccine‐derived polioviruses now exceed 3,000 cases reported by 39 countries. In 2022 (as of April 25, 2023), 20 countries reported detection of cases and nine other countries reported environmental surveillance detection, but no reported cases. Recent development of a genetically modified novel type 2 OPV (nOPV2) may help curb the generation of neurovirulent vaccine‐derived strains; its use since 2021 under Emergency Use Listing is limited to outbreak response activities. Prior modeling studies showed that the expected trajectory for global type 2 viruses does not appear headed toward eradication, even with the best possible properties of nOPV2 assuming current outbreak response performance. Continued persistence of type 2 poliovirus transmission exposes the world to the risks of potentially high‐consequence events such as the importation of virus into high‐transmission areas of India or Bangladesh. Building on prior polio endgame modeling and assuming current national and GPEI outbreak response performance, we show no probability of successfully eradicating type 2 polioviruses in the near term regardless of vaccine choice. We also demonstrate the possible worst‐case scenarios could result in rapid expansion of paralytic cases and preclude the goal of permanently ending all cases of poliomyelitis in the foreseeable future. Avoiding such catastrophic scenarios will depend on the development of strategies that raise population immunity to type 2 polioviruses. [ABSTRACT FROM AUTHOR]

Due to the very low, but nonzero, paralysis risks associated with the use of oral poliovirus vaccine (OPV), eradicating poliomyelitis requires ending all OPV use globally. The Global Polio Eradication Initiative (GPEI) coordinated cessation of Sabin type 2 OPV (OPV2 cessation) in 2016, except for emergency outbreak response. However, as of early 2023, plans for cessation of bivalent OPV (bOPV, containing types 1 and 3 OPV) remain undefined, and OPV2 use for outbreak response continues due to ongoing transmission of type 2 polioviruses and reported type 2 cases. Recent development and use of a genetically stabilized novel type 2 OPV (nOPV2) leads to additional potential vaccine options and increasing complexity in strategies for the polio endgame. Prior applications of integrated global risk, economic, and poliovirus transmission modeling consistent with GPEI strategic plans that preceded OPV2 cessation explored OPV cessation dynamics and the evaluation of options to support globally coordinated risk management efforts. The 2022–2026 GPEI strategic plan highlighted the need for early bOPV cessation planning. We review the published modeling and explore bOPV cessation immunization options as of 2022, assuming that the GPEI partners will not support restart of the use of any OPV type in routine immunization after a globally coordinated cessation of such use. We model the potential consequences of globally coordinating bOPV cessation in 2027, as anticipated in the 2022–2026 GPEI strategic plan. We do not find any options for bOPV cessation likely to succeed without a strategy of bOPV intensification to increase population immunity prior to cessation. [ABSTRACT FROM AUTHOR]

Background: Despite multiple revisions of targets and timelines in polio eradication plans since 1988, including changes in supplemental immunization activities (SIAs) that increase immunity above routine immunization (RI) coverage, poliovirus transmission continues as of 2024. Methods: We reviewed polio eradication plans and Global Polio Eradication Initiative (GPEI) annual reports and budgets to characterize key phases of polio eradication, the evolution of poliovirus vaccines, and the role of SIAs. We used polio epidemiology to provide context for successes and failures and updated prior modeling to show the contribution of SIAs in achieving and maintaining low polio incidence compared to expected incidence for the counterfactual of RI only. Results: We identified multiple phases of polio eradication that included shifts in targets and timelines and the introduction of different poliovirus vaccines, which influenced polio epidemiology. Notable shifts occurred in GPEI investments in SIAs since 2001, particularly since 2016. Modeling results suggest that SIAs play(ed) a key role in increasing (and maintaining) high population immunity to levels required to eradicate poliovirus transmission globally. Conclusions: Shifts in polio eradication strategy and poliovirus vaccine usage in SIAs provide important context for understanding polio epidemiology, delayed achievement of polio eradication milestones, and complexity of the polio endgame. [ABSTRACT FROM AUTHOR]

Pakistan and Afghanistan pose risks for international transmission of polioviruses as the last global reservoir for wild poliovirus type 1 (WPV1) and a reservoir for type 2 circulating vaccine‐derived polioviruses (cVDPV2s). Widespread transmission of WPV1 and cVDPV2 in 2019–2020 and resumption of intensive supplemental immunization activities (SIAs) in 2020–2021 using oral poliovirus vaccine (OPV) led to decreased transmission of WPV1 and cVDPV2 as of the end of 2021. Using an established dynamic disease transmission model, we explore multiple bounding scenarios with varying intensities of SIAs using bivalent OPV (bOPV) and/or trivalent tOPV (tOPV) to characterize potential die out of transmission. This analysis demonstrates potential sets of actions that may lead to elimination of poliovirus transmission in Pakistan and/or Afghanistan. Some modeled scenarios suggest that Pakistan and Afghanistan could increase population immunity to levels high enough to eliminate transmission, and if maintained, achieve WPV1 and cVDPV2 elimination as early as 2022. This requires intensive and proactive OPV SIAs to prevent transmission, instead of surveillance followed by reactive outbreak response. The reduction of cases observed in 2021 may lead to a false sense of security that polio has already or soon will die out on its own, but relaxation of immunization activities runs the risk of lowering population immunity to, or below, the minimum die‐out threshold such that transmission continues. Transmission modeling may play a key role in managing expectations and supporting future modeling about the confidence of no virus circulation in anticipation of global certification decisions. [ABSTRACT FROM AUTHOR]

Since 2013, wild poliovirus (WPV) transmission occurred only for type 1 (WPV1). Following several years of increasing reported incidence (2017–2019) and programmatic disruptions caused by COVID‐19 (early 2020), Pakistan and Afghanistan performed a large number of supplementary immunization activities (late 2020–2021). This increased intensity of immunization, following widespread transmission, substantially decreased WPV1 cases and positive environmental samples during 2021. Modeling the potential for undetected circulation of WPV1 after apparent interruption can support regional and global decisions about certification of the eradication of indigenous WPV1 transmission. We apply a stochastic model to estimate the confidence about no circulation (CNC) of WPV1 in Pakistan and Afghanistan as a function of time since the last reported case and/or positive environmental sample. Exploration of different assumptions about surveillance quality suggests a range for CNC for WPV1 as a function of time since the last positive surveillance signal, and supports the potential use of a time with no evidence of transmission of less than 3 years as sufficient to assume die out in the context of good acute flaccid paralysis (AFP) surveillance. We show high expected CNC based on AFP surveillance data alone, even with imperfect surveillance and some use of inactivated poliovirus vaccine masking the ability of AFP surveillance to detect transmission. Ensuring high quality AFP and environmental surveillance may substantially shorten the time required to reach high CNC. The time required for high CNC depends on whether immunization activities maintain high population immunity and the quality of surveillance data. [ABSTRACT FROM AUTHOR]