ABSTRACT

The Pan American Health Organization (PAHO) and its Member States have been leading the efforts to eradicate wild poliovirus in the Region of Americas since smallpox's successful elimination in 1971. The region became the first to be certified free of wild poliovirus in 1994. However, in July 2022, an unvaccinated patient with no recent travel history was diagnosed with poliomyelitis in the United States of America. In response to the emergence of a circulating vaccine-derived poliovirus in the United States, PAHO established the Polio Incident Management Support Team. This team has been coordinating response efforts, focusing on: coordination, planning, and monitoring; risk communication and community engagement; surveillance and case investigation; vaccination; and rapid response. In this paper, we identified and documented best practices observed following establishment of the Incident Management Support Team (September 2022–2023) through a comprehensive review and analysis of various data sources and country-specific data from the polio surveillance dashboard. The aim was to share these best practices, highlighting technical support and implementation of polio measures by Member States. Despite several challenges, the Americas region remains polio-free. Polio risk is declining, with a July 2023 assessment showing fewer countries at medium, high, and very high risk. This progress reflects improved immunization coverage, surveillance, containment, health determinants, and outbreak preparedness and response. The PAHO Polio Incident Management Support Team has played a key role in supporting these efforts.

Keywords
Poliomyelitis; vaccination coverage; surveillance; Pan American Health Organization; Americas

RESUMEN

La Organización Panamericana de la Salud (OPS) y sus Estados Miembros han liderado los esfuerzos para erradicar el poliovirus salvaje en la Región de las Américas desde la eliminación exitosa de la viruela en 1971. En 1994, la Región fue la primera en obtener la certificación de libre del poliovirus salvaje. Sin embargo, en julio del 2022, se diagnosticó poliomielitis a un paciente de Estados Unidos de América no vacunado y sin antecedentes de viajes recientes. Para responder a la aparición de un poliovirus circulante derivado de la vacuna en ese país, la OPS creó el equipo de apoyo a la gestión de incidentes de poliomielitis. Este equipo ha asumido la coordinación de los esfuerzos de respuesta y se ha centrado en la coordinación, la planificación y seguimiento; la comunicación de riesgos y la participación de la comunidad; la vigilancia e investigación de casos; la vacunación; y la respuesta rápida. En este artículo, se determinan y documentan las mejores prácticas observadas después de la creación del equipo de apoyo a la gestión de incidentes (septiembre del 2022-2023) mediante una revisión y un análisis pormenorizados de datos procedentes de diversas fuentes y de datos específicos de los países del panel de vigilancia de la poliomielitis. El objetivo fue poner en común estas mejores prácticas y resaltar el apoyo técnico y la aplicación de medidas contra la poliomielitis por parte de los Estados Miembros. A pesar de los diversos desafíos, la Región de las Américas se mantiene libre de poliomielitis. El riesgo de esta enfermedad es cada vez menor, y la evaluación de julio del 2023 muestra una disminución del número de países con un riesgo medio, alto o muy alto. Este progreso refleja la mejora de la cobertura de inmunización, la vigilancia, la contención, los determinantes de la salud y la preparación y respuesta ante brotes. El equipo de apoyo a la gestión de incidentes relacionados con la poliomielitis de la OPS ha desempeñado un papel fundamental para brindar apoyo a estas iniciativas.

Palabras clave
Poliomielitis; cobertura de vacunación; vigilancia; Organización Panamericana de la Salud; Américas

RESUMO

Desde a eliminação bem-sucedida da varíola em 1971, a Organização Pan-Americana da Saúde (OPAS) e seus Estados Membros têm estado à frente de iniciativas para erradicar o poliovírus selvagem na Região das Américas. Em 1994, a região foi a primeira do mundo a ser certificada como livre do poliovírus selvagem. Entretanto, em julho de 2022, um paciente não vacinado e sem histórico de viagens recentes foi diagnosticado com poliomielite nos Estados Unidos da América. Em resposta ao surgimento de um poliovírus derivado de vacina circulante nos Estados Unidos, a OPAS criou a Equipe de Apoio à Gestão de Incidentes de Poliomielite. A equipe vem administrando os esforços de resposta, concentrando-se em: coordenação, planejamento e monitoramento; comunicação de risco e envolvimento da comunidade; vigilância e investigação de casos; vacinação; e resposta rápida. Neste documento, identificamos e documentamos as melhores práticas observadas após a criação da Equipe de Apoio à Gestão de Incidentes (setembro de 2022 a 2023) por meio de uma revisão e análise abrangentes de diversas fontes de dados e dados específicos de cada país fornecidos por meio do painel de vigilância da poliomielite. O objetivo foi compartilhar essas melhores práticas, destacando o apoio técnico e a implementação de medidas contra a poliomielite pelos Estados Membros. Apesar de vários desafios, a Região das Américas continua livre da poliomielite. Um levantamento de julho de 2023 demonstrou que o risco da poliomielite vem diminuindo, com menos países com risco médio, alto ou muito alto. Essa evolução é resultado de melhoras na cobertura vacinal, vigilância, contenção, preparação, determinantes de saúde e resposta a surtos. A Equipe de Apoio à Gestão de Incidentes de Poliomielite da OPAS foi fundamental para apoiar esses esforços.

Palavras-chave
Poliomielite; cobertura vacinal; vigilancia; Organização Pan-Americana da Saúde; América

After the elimination of smallpox from the Region of the Americas in 1971, the Pan American Health Organization (PAHO) and its Member States led an initiative to eliminate all wild poliovirus types (WPV) from the region. They coordinated efforts to implement high-quality vaccination campaigns, surveillance systems, and other control measures. As a result, the last case of polio due to WPV occurred in Peru in 1991 and in 1994, the Region of the Americas became the first World Health Organization (WHO) region certified as having successfully interrupted WPV transmission (¹1. Centers for Disease Control and Prevention. Progress toward global poliomyelitis eradication, 1985–1994. MMWR Morb Mortal Wkly Rep. 1995;44(14):273–5, 81.–³3. Pedreira C, Thrush E, Rey-Benito G, Chévez AE, Jauregui B. The path towards polio eradication over 40 years of the Expanded Program on Immunization in the Americas. Rev Panam Salud Publica. 2017;41:e154. https://doi.org/10.26633/RPSP.2017.154
https://doi.org/10.26633/RPSP.2017.154... ).

Since the certification, countries in the region have continued vaccination efforts and epidemiological surveillance of cases of acute flaccid paralysis (AFP) to: 1) sustain immunity against poliovirus; 2) detect polio cases (if any); 3) ensure a timely response and control; and 4) monitor the effectiveness of their vaccination programs. However, with more than 2 years of the coronavirus disease 2019 (COVID-19) pandemic, health systems have faced challenges in maintaining a polio-free status. One of the main consequences has been the exacerbation of the pre-existing decline in vaccination coverage, including polio vaccination (⁴4. World Health Organization and United Nations Children’s Fund. WHO/UNICEF estimates of national immunization coverage [internet]. WHO/UNICEF; 2023 [cited 2023 Jul 26]. Available from: https://www.who.int/teams/immunization-vaccines-and-biologicals/immunization-analysis-and-insights/global-monitoring/immunization-coverage/who-unicef-estimates-of-national-immunization-coverage
https://www.who.int/teams/immunization-v... , ⁵5. World Health Organization. Third round of the global pulse survey on continuity of essential health services during the COVID-19 pandemic: November–December 2021: interim report, 7 February 2022. Geneva: WHO: 2022 [cited 2024 Jan 27]. Available from: https://iris.who.int/handle/10665/351527
https://iris.who.int/handle/10665/351527... ).

Alongside the challenges of low routine immunization coverage, the introduction of multiple doses of inactivated poliovirus vaccine in the region was unexpectedly affected by a global supply shortage immediately after replacing the trivalent oral polio vaccine with the bivalent oral polio vaccine (⁶6. Sutter RW, Cochi SL. Inactivated poliovirus vaccine supply shortage: is there light at the end of the tunnel? J Infect Dis. 2019;220(10):1545–6. https://doi.org/10.1093/infdis/jiy739
https://doi.org/10.1093/infdis/jiy739... ). The shortages of inactivated poliovirus vaccine stocks between 2016 and 2019 resulted in fewer vaccinations administered, potentially leading to decreased immunity against poliovirus, particularly for the type 2 strain (⁷7. Anand A, Molodecky NA, Pallansch MA, Sutter RW. Immunogenicity to poliovirus type 2 following two doses of fractional intradermal inactivated poliovirus vaccine: a novel dose sparing immunization schedule. Vaccine. 2017;35(22):2993–8. https://doi.org/10.1016/j.vaccine.2017.03.008
https://doi.org/10.1016/j.vaccine.2017.0... , ⁸8. Bandyopadhyay AS, Gast C, Rivera L, Sáez-Llorens X, Oberste MS, Weldon WC, et al. Safety and immunogenicity of inactivated poliovirus vaccine schedules for the post-eradication era: a randomised open-label, multicentre, phase 3, non-inferiority trial. Lancet Infect Dis. 2021;21(4):559–68. https://doi.org/10.1016/S1473-3099(20)30555-7
https://doi.org/10.1016/S1473-3099(20)30... ). These cohorts could have been more susceptible to the disease as the humoral immunity depends primarily on routine immunization coverage.

In July 2022, an unvaccinated patient with no recent travel history was diagnosed with poliomyelitis in the state of New York, United States of America. The case was initially confirmed as a type 2 vaccine-derived poliovirus (VDPV2) by the United States Centers for Disease Control and Prevention. However, subsequent investigations found genetic sequences related to the virus in environmental wastewater samples collected from Rockland County, New York, as well as other nearby counties (⁹9. Pan American Health Organization. Epidemiological update. Detection of a circulating vaccine-derived poliovirus type 2 (VDPV2) in the United States: Considerations for the Region of the Americas. Washington, D.C.: PAHO: 2022 [cited 2024 Jan 27]. Available from: https://www.paho.org/en/documents/epidemiological-update-detection-circulating-vaccine-derived-poliovirus-type-2-vdpv2
https://www.paho.org/en/documents/epidem... –¹¹11. Pan American Health Organization. Epidemiological update poliomyelitis in the Region of the Americas – 23 March 2023. Washington, D.C.: PAHO; 2023 [cited 2024 Jan 27]. Available from: https://www.paho.org/en/documents/epidemiological-update-poliomyelitis-region-americas-23-march-2023
https://www.paho.org/en/documents/epidem... ). These genetic variants of VDPV2, imported from an unknown source, were also detected in wastewater in Jerusalem, Israel and London, United Kingdom of Great Britain and Northern Ireland (¹²12. John TJ, Dharmapalan D. Lessons from vaccine-related poliovirus in Israel, UK and USA. Vaccines (Basel). 2022;10(11):1969. https://doi.org/10.3390/vaccines10111969
https://doi.org/10.3390/vaccines10111969... ). After these findings, wastewater surveillance was initiated, and ongoing testing confirmed the presence of vaccine-derived poliovirus in multiple samples collected from Rockland, Orange, Sullivan, and Nassau counties, and New York City in New York State. Due to the detection of environmental viral sequences (collected on 3 August and 11 August 2022) containing more than five nucleotide changes, and both linked to the case reported in Rockland County, these viruses were now being classified as so-called circulating VDPV2 (cVDPV2). Canada also conducted wastewater analysis to search for the virus. By August 2022, the National Microbiology Laboratory of Canada had detected two positive samples for VDPV2, which had slight genetic differences compared to the Sabin virus type 2 (¹¹11. Pan American Health Organization. Epidemiological update poliomyelitis in the Region of the Americas – 23 March 2023. Washington, D.C.: PAHO; 2023 [cited 2024 Jan 27]. Available from: https://www.paho.org/en/documents/epidemiological-update-poliomyelitis-region-americas-23-march-2023
https://www.paho.org/en/documents/epidem... , ¹³13. World Health Organization. Detection of circulating vaccine derived polio virus 2 (cVDPV2) in environmental samples – the United Kingdom of Great Britain and Northern Ireland and the United States of America. Geneva: WHO; 2022 [cited 2024 Jan 27]. Available from: https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON408
https://www.who.int/emergencies/disease-... ).

The cVDPV2 outbreak represented a significant risk that polio could be reintroduced into other countries in the Americas. Therefore, intensified vaccination efforts were urgently needed to ensure an optimal level of population immunity, and robust epidemiological surveillance needed to be implemented to detect and investigate AFP cases promptly.

On September 14, 2022, PAHO activated its Special Emergency Procedures and established an incident management support team (IMST) for polio. The objectives of the team were to consolidate the Organization’s support to countries, enhance preparedness, and facilitate rapid response actions to address the polio situation. Additionally, the 30th Pan American Sanitary Conference, held in Washington D.C. on 26–30 September 2022, centered on assisting Member States in polio mitigation. PAHO offered technical guidance to high-risk nations, in collaboration with the Technical Advisory Group on Vaccine-Preventable Diseases, advising on vaccination improvement, surveillance enhancement, and outbreak readiness. Recommendations from PAHO and the Technical Advisory Group included boosting vaccination coverage, improving surveillance, and preparing for outbreaks. A notable collaboration took place with the United States during a cVDPV2 outbreak in New York State.

The main objective of this paper was to disseminate the best practices observed as a result of implementing the IMST for polio response. It highlights these practices, the technical support provided to Member States, and their implementation of the recommendations the IMST. Ultimately, we hope to enable the use of these best practices to enhance future polio response efforts and strengthen overall disease management strategies.

METHODS

We systematically identified and documented best practices (September 2022–2023) through a comprehensive review and analysis of various data sources, including internal PAHO reports, presentations and documents, and country-specific data from the polio surveillance dashboard. The polio surveillance dashboard is an open online platform developed as part of the response (¹⁴14. Pan American Health Organization. Polio surveillance dashboard [internet]. PAHO; 2022 [cited 2024 Jan 27]. Available from: https://www.paho.org/en/polio-surveillance-dashboard
https://www.paho.org/en/polio-surveillan... ).

Analysis of the dashboard data, particularly in areas such as risk/susceptibility analysis, AFP surveillance performance indicators, and polio vaccination coverage, helped identify countries with higher susceptibility to polio outbreaks and initiatives focused on addressing challenges related to polio eradication. How programs/interventions overcame difficulties and adapted to challenges by consistently demonstrating high performance suggested potential best practices.

RESULTS AND DISCUSSION

Polio situation update

On March 21, 2023, Peru notified PAHO and WHO of a confirmed case of VDPV type 1 (VDPV1) in a 14-month-old child from an indigenous community. The investigation and clinical evaluation ruled out the possibility of an immunocompromised patient. The complete sequence of the VP1 region of the VDPV1 viral genome showed 31 nucleotide differences compared to the Sabin 1 virus and it was not genetically related to any other VDPV1 previously sequenced, including those currently circulating in countries with cVDPV1 outbreaks. Field investigations identified two additional AFP cases, which were evaluated and discarded as polio cases. Polio vaccination coverage in Peru has been less than 95% in recent years, with about 45% of districts reporting coverage less than 80%. Gaps also exist in AFP surveillance indicators in the past 3 years, that is low AFP rate, inadequate stool collection, and delayed investigation of AFP cases (¹¹11. Pan American Health Organization. Epidemiological update poliomyelitis in the Region of the Americas – 23 March 2023. Washington, D.C.: PAHO; 2023 [cited 2024 Jan 27]. Available from: https://www.paho.org/en/documents/epidemiological-update-poliomyelitis-region-americas-23-march-2023
https://www.paho.org/en/documents/epidem... ).

Polio IMST

The polio IMST is a multidisciplinary team that consists of individuals selected based on their specific knowledge/skills in relation to responding to polio incidents. Initially, the team had a six-pillar structure (Figure 1). Later, this was restructured to integrate “access to supplies and technologies” and “enabling functions” under one pillar, namely “coordination, planning, and monitoring”.

Lessons and polio best practices

Pillar 1: coordination, planning, and monitoring. The IMST on polio published and disseminated PAHO’s Strategic Response Plan and Appeal for polio to address the ongoing emergency declaration. The PAHO/WHO polio response strategy aims to rapidly enable Member States to increase vaccination coverage and improve surveillance performance. The strategy advocates a whole-of-society approach to reduce the risk of a polio outbreak and ensure that national health systems and services are prepared to detect and respond to poliovirus events or outbreaks. The Strategic Response Plan and Appeal for polio is structured around three strategic objectives: 1) advocacy for an all-sector approach; 2) technical cooperation for risk communication; and 3) technical cooperation for risk mitigation.

To raise awareness of the current situation and highlight the risk of a possible outbreak, the IMST on polio convened a meeting for managers of the Expanded Programme on Immunization (EPI). Participants from 36 countries and territories attended, including from the four very high-risk countries of 2022 – Brazil, Dominican Republic, Haiti, and Peru (¹⁵15. Pan American Health Organization. 14ª Reunión de la Comisión Regional de Certificación de la Erradicación de la Poliomielitis en la Región de las Américas – Informe de la reunion [14th Meeting of the Regional Certification Commission for Poliomyelitis Eradication in the Region of the Americas – Report of the meeting]. Washington, D.C.: PAHO; 2022 [cited 2024 Jan 27]. Available from: https://www.paho.org/es/documentos/14a-reunion-comision-regional-certificacion-erradicacion-poliomielitis-region-americas#:~:text=La%2014%C2%AA%20Reuni%C3%B3n%20de%20la,al%208%20de%20julio%202022
https://www.paho.org/es/documentos/14a-r... ). Moreover, to support continued high-level advocacy efforts, the polio IMST organized 10 individual briefing sessions with very high-risk and high-risk countries to review surveillance, vaccination coverage, and preparedness.

In the context of the case identified in Peru, the polio IMST provided support for surge capacity efforts to the PAHO country office by allocating additional funds and personnel. PAHO also engaged at the highest levels of government to ensure that the event was given due importance in the context of multiple emergencies in the country.

Pillar 2: risk communication and community engagement. The IMST met with Canada’s Public Health Agency to coordinate cVDPV2 messaging. This effort allowed PAHO and Canada to better handle media requests and questions from the public. A workshop in Panama in March 2023 trained health workers and communicators from Central America, Cuba, and the Dominican Republic on demand-driven communication strategies for polio and other vaccines. Additionally, a workshop on June 22, aligned with the Global Polio Eradication Initiative (GPEI) standard operating procedures (SOPs) for responding to a poliovirus event or outbreak and surveillance recommendations, trained Peruvian health professionals in risk communication and community engagement for indigenous communities.

A package of communication materials was developed for countries on prevention and response to a polio outbreak. PAHO provided high-risk countries with adaptable social media cards, historical videos on eliminated diseases, and campaign materials to raise funds.

Key documents of the GPEI, such as the novel oral polio vaccine type 2 (nOPV2) application form, cold chain requirements, and vaccine management in the context of nOPV2 use, were translated into Spanish to improve access to information for Member States. All these materials are available on the PAHO website, which is updated regularly to include relevant information.

Pillar 3: surveillance and case investigation. Continuous communication with countries and virtual meetings emphasized the importance of strengthening surveillance systems. These efforts have yielded positive results, as surveillance performance in the region has shown improvement compared to previous years. The acute AFP rate had been lower than the target of 1 case per 100 000 children younger than 15 years up to 2020. The latest available information (as of August 12, 2023) on the AFP rate for 2022 was 1.27 cases per 100 000. Furthermore, the percentage of cases investigated within 48 hours for 2022 was 91%, which is higher than the expected 80%, and the percentage of cases with an adequate sample was 75%, which is still less than the expected target but shows an improvement when compared to previous years (¹⁴14. Pan American Health Organization. Polio surveillance dashboard [internet]. PAHO; 2022 [cited 2024 Jan 27]. Available from: https://www.paho.org/en/polio-surveillance-dashboard
https://www.paho.org/en/polio-surveillan... , ¹⁶16. Global Polio Eradication Initiative. Polio Now 2023. Geneva: GPEI; 2023., ¹⁷17. Pan American Health Organization. Polio bulletin. Washington, D.C.: PAHO; 2023 [cited 2024 Jan 27]. Available from: www.paho.org/immunization/PolioBulletin
www.paho.org/immunization/PolioBulletin... ).

Among the high- and very high-risk countries, five countries – Argentina, Bolivia (Plurinational State of), Brazil, Panama, and Venezuela (Bolivarian Republic of) – reported an AFP rate higher than the target, and Guatemala is very close to the target. However, the other high-risk countries (Dominican Republic, Ecuador, Haiti, and Peru) and the Caribbean Subregion, which includes Bahamas and Suriname, reported an AFP rate of 70% or lower (¹⁴14. Pan American Health Organization. Polio surveillance dashboard [internet]. PAHO; 2022 [cited 2024 Jan 27]. Available from: https://www.paho.org/en/polio-surveillance-dashboard
https://www.paho.org/en/polio-surveillan... ).

The surveillance performance in the countries has been actively monitored with a dashboard that includes information for countries as well as management data for the IMST (Figure 2). Furthermore, so-called hot cases, which show at least three of five parameters (younger than 5 years, fewer than three doses of polio vaccine received or unknown vaccination status, rapid progression of paralysis, asymmetric paralysis, and fever at onset of clinical presentation) have been closely monitored and investigated in coordination with the countries due to their potential to signal ongoing transmission of the virus in an area or community. The IMST hosted a webinar for more than 500 healthcare professionals on polio surveillance, management, and patient evaluation (¹⁸18. Pan American Health Organization. Actualización en la vigilancia, el manejo clínico y la evaluación neurológica de casos de parálisis flácida aguda (PFA) [Update on surveillance, clinical management and neurological evaluation of cases of acute flaccid paralysis (AFP)]. PAHO: 2023 [cited 2024 Jan 27]. Available from: https://www.paho.org/es/eventos/actualizacion-vigilancia-manejo-clinico-evaluacion-neurologica-casos-paralisis-flacida
https://www.paho.org/es/eventos/actualiz... ).

Pillar 4: vaccination strategy. During the regional meeting convened by the Polio IMST with EPI managers, the team outlined the different strategies to address polio vaccination catch-up, both for intensive vaccination activities and for the routine program. Additionally, the IMST developed guidelines for the elaboration of polio risk mitigation plans based on risk assessment using a root cause analysis by component at the municipal level. PAHO also supported the development of a set of exercises to support countries in the preparation of polio risk mitigation plans at the municipal/district level and microplanning of the vaccination response based on the 2022 GPEI SOPs for responding to a poliovirus event or outbreak (¹⁹19. Standard operating procedures: responding to a poliovirus event or outbreak, version 4. Geneva: World Health Organization on behalf of the Global Polio Eradication Initiative; 2022 [cited 2024 Jan 27]. Available from: https://iris.who.int/handle/10665/363627
https://iris.who.int/handle/10665/363627... ).

The inventory of the bivalent oral polio vaccine and inactivated poliovirus vaccine in the countries was constantly monitored. PAHO's Revolving Fund for Vaccine Access guaranteed the extension of the line of credit to ensure vaccine availability at all times in all countries and territories that procure their vaccine through the Fund (²⁰20. Cornejo S, Chevez A, Ozturk M, Vargas O, Behrensen F, Solano L, et al. El Fondo Rotatorio para el acceso a las vacunas de la Organización Panamericana de la Salud: 43 años respondiendo al programa regional de inmunizaciones [The Pan American Health Organization's Revolving Fund for access to vaccines: 43 years responding to the regional immunization program]. Rev Panam Salud Publica. 2023;47:e50. https://doi.org/10.26633/RPSP.2023.50
https://doi.org/10.26633/RPSP.2023.50... ). The Fund also maintained close communication with vaccine manufacturers to ensure timely deliveries.

Pillar 5: rapid response. The translation of the GPEI SOPs for responding to a poliovirus event or outbreak was finalized. In addition, a checklist was prepared to guide countries in developing or updating their national outbreak response plans. The importance of an interdisciplinary approach at the national level in the process of updating plans was emphasized, including the involvement of the National Immunization Technical Group of Experts and National Certification Committees for Eradication.

Based on recommendations from the GPEI SOPs for responding to a poliovirus event or outbreak, the Polio IMST identified an initial list of experts to structure rapid response teams. This allowed PAHO, together with the Stop Transmission of Polio team, to promptly extend technical support to Peru after the detection of the VDPV1.

PAHO reviewed and adapted/updated the simulation exercise guides for a polio outbreak 2015 according to the GPEI’s SOPs. An exercise was organized for health authorities and operational levels of Peru, which included the new standardized case definitions established by WHO for AFP. The IMST also continued to engage with the countries with a high- and very high-risk of a polio event or outbreak in line with the standards of the Regional Certification Commission for the Polio Endgame in the Region of the Americas.

Limitations

Our review has some limitations. First, it relied on internal PAHO documents and reports. While these documents offer a trustworthy source of information, this approach could limit the identification of best practices that are not formally documented or readily accessible. Second, the data from the polio dashboard is based on surveillance data reported by PAHO Member States to the regional office. There may be delays in reporting, underreporting of cases, and differences in data collection and reporting methodologies across countries. Efforts to improve data quality, standardize reporting practices, and expand data collection beyond surveillance data have helped address these limitations. Lastly, a cost analysis of interventions was not done, which raises questions about their long-term sustainability.

CONCLUSIONS

In 2021, only 80% of children had the necessary third dose of the polio vaccine, compared with 88% in 2018. Additionally, surveillance activities were severely affected by the COVID-19 pandemic in most countries, thus increasing the risk of polio circulation after the importation of a WPV1 or VDPV, or VDPV emergence. Despite the low vaccination coverage and health system challenges, the region has maintained its polio-free status with the support of PAHO and its IMST. In 2022, countries and territories in the Americas managed to halt the decline in polio vaccination coverage that the region had been experiencing. Based on the WHO and United Nations Children’s Fund estimates of national immunization coverage, polio3 coverage in the Americas has risen to 83%. A July 2023 assessment by the Regional Certification Commission found a decrease in the number of countries at medium-, high-, and very high-risk of poliovirus circulation compared with previous evaluations. This improved risk profile is attributed to more countries becoming low risk, as well as improvements in immunization coverage, surveillance, containment, health determinants, and outbreak preparedness and response.

The IMST has been instrumental in advocating for immunization programs, addressing barriers to vaccination, supporting surveillance efforts, and collaborating with countries to mitigate polio risks. The Americas must maintain and strengthen vaccination and surveillance efforts to build on recent progress and ensure a polio-free future for generations to come.

Disclaimer.

The authors hold sole responsibility for the views expressed in the manuscript, which may not necessarily reflect the opinion or policy of the Revista Panamericana de Salud Pública / Pan American Journal of Public Health and/or those of the Pan American Health Organization and the World Health Organization.

Acknowledgements.

We thank Pilar Ramon-Pardo, Lic. Evelyn Lopez and all members of the IMST for their contributions upon which this report is based. In addition, we thank Ivy Lorena Talavera, Patricia Arce, Mariana Landa, and Maria Cecilia Razzotti from the Guatemala STOP team for their valuable technical expertise and assistance to the VDPV1 event in Peru. We also thank PAHO’s immunization focal points, colleagues from the EPI, and all the healthcare workers in the region who work tirelessly to keep the region free of polio.

REFERENCES

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