Is Climate Change Undermining Polio Eradication Efforts in Sindh, Pakistan? A Comprehensive Evidence from 2015–2025

Is Climate Change Undermining Polio Eradication Efforts in Sindh, Pakistan? 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A Comprehensive Evidence from 2015–2025 Dr. Sharaf Uddin Behan, Dr. Mishal Akhund, Ms. Huma Nisar, Dr. Nabeela Hamza, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9254205/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract In Sindh, Karachi and Hyderabad, have remained persistent reservoirs for Wild Poliovirus Type 1 (WPV1). Climate change acts as a significant force multiplier for WPV1 transmission. Traditional eradication strategies mainly focus on vaccine hesitancy and operational gaps. However, the role of climate change remains underexplored. This review examines the impact of climatic variables on polio eradication efforts in Sindh from 2015 to 2025. A narrative review with PRISMA guidelines, have covered heatwaves, flooding, precipitation changes, vaccination disruptions, and poliovirus risks. Data came from PubMed, The Lancet, WHO surveillance reports, and Pakistan Meteorological Department datasets. The 2022 Pakistan floods damaged 888 health facilities, disrupting polio vaccination campaigns and contributing to a surge in polio cases from 1 in 2021 to 20 in 2022. Extreme weather events showed a strong temporal association with transmission spikes, with SIAs reduced by 34% in Northern Sindh post-floods. Climate-induced disruptions, including compromised cold-chain logistics and water/sanitation infrastructure damage, exacerbated poliovirus transmission and hindered eradication efforts. Eradication strategies must shift from static models to climate-resilient systems. Failure to integrate climatological data into public health planning threatens the global eradication goal. Climate change Poliovirus Polio Eradication Immunization Sindh Heatwaves Floods Environmental Surveillance Vaccination Campaigns Population Displacement Figures Figure 1 1. Introduction 1.1 Global Polio Eradication Progress and Pakistan's Persistent Challenge Pakistan remains one of only two countries with endemic wild poliovirus type 1 (WPV1) transmission, with Sindh province constituting a persistent viral reservoir characterized by substantial gaps in supplementary immunization activities quality [ 1 , 2 , 3 ]. The Global Polio Eradication Initiative (GPEI) has achieved a remarkable 99% reduction in polio incidence since 1988, yet eradication remains elusive in Pakistan [ 1 , 4 ]. Sindh province serves as a critical transmission hub, where Karachi's high-density slums and Northern Sindh's rural expanses sustain ongoing poliovirus circulation [ 2 , 3 ]. Historically, epidemiological literature has primarily attributed polio persistence in the region to vaccine hesitancy clusters and security-related operational challenges [ 2 , 5 ]. 1.2 Climate Change as an Emerging Environmental Determinant While traditional polio eradication strategies have focused on vaccine hesitancy and operational barriers, anthropogenic climate change has intensified multiple environmental stressors across the South Asian region, manifesting as extreme heatwaves, altered monsoon precipitation patterns, and recurrent catastrophic flooding [ 6 , 7 , 8 ]. These climatic shifts directly disrupt vaccination campaign implementation and threaten to undermine progress toward global eradication [ 6 , 8 ]. Pakistan ranked among the top ten countries most affected by climate change between 2000 and 2019 [ 7 ], and the period 2015–2025 witnessed unprecedented climatic volatility in Sindh, including the catastrophic 2022 monsoon floods and recurrent severe heatwaves [ 9 , 10 , 11 ]. 1.3 The 2022 Monsoon Floods: A Critical Epidemiological Event The 2022 monsoon floods that inundated approximately one-third of Pakistan displaced over 33 million people nationwide, damaged critical healthcare infrastructure, and provided clear empirical evidence of the extent to which extreme weather events compromise routine immunization services [ 3 , 9 , 10 ]. This catastrophic event demonstrated that climate-related infrastructure damage creates operational barriers distinct from traditional refusal or security-based obstacles [ 9 ]. 1.4 Literature Gap and Research Rationale Despite the emerging global consensus that climate change represents a critical threat to public health infrastructure, the specific mechanisms through which climatic variables—including temperature fluctuations, precipitation variability, and flood-induced population displacement—contribute to polio eradication challenges in Sindh province remain inadequately characterized in the epidemiological literature [ 6 , 8 , 12 ] This gap is particularly significant given the known associations between environmental factors and poliovirus amplification [ 13 ]. The rationale for this systematic review is to bridge clinical epidemiology with environmental science, integrating evidence that addresses how climate-driven disruptions interact with traditional polio persistence barriers. 1.5 Study Hypothesis and Objectives We hypothesize that climate change undermines polio eradication through three distinct but interconnected mechanisms: infrastructure damage affecting immunization service delivery, mass population displacement creating new transmission pathways, and altered environmental conditions affecting poliovirus survival kinetics [ 5 , 12 , 13 ] This review synthesizes evidence from 2015 onwards on the convergent impacts of climate-driven environmental disruptions and traditional eradication barriers on poliomyelitis persistence in Sindh province, with the primary objective of identifying evidence-based, climate-resilient strategies to accelerate the final stages of global polio eradication. 2. Methodology 2.1 Review Design and Reporting Standards This simple narrative review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [ 14 ] to ensure methodological rigor and transparent reporting of evidence synthesis procedures. 2.2 Information Sources and Literature Search Strategy A comprehensive literature search was performed across multiple electronic databases—PubMed, The Lancet, and EMBASE—supplemented by authoritative global health surveillance databases including the Global Polio Eradication Initiative (GPEI) surveillance platform [ 1 ], World Health Organization (WHO) epidemiological reports [ 3 ], and Pakistan Meteorological Department climate datasets [ 10 ]. The search encompassed the temporal period from 2015 to 2025 to capture contemporary climate-health dynamics in the endemic polio context and ensure inclusion of recent evidence reflecting post-2020 epidemiological patterns. 2.3 Eligibility Criteria 2.3.1 Inclusion criteria Studies were included if they met the following criteria: Published or reported between 2015 and 2025 (to capture contemporary climate-health dynamics and post-2020 epidemiological patterns). Focused on wild poliovirus type 1 (WPV1) epidemiology, case detection, or environmental surveillance (sewage sampling and wastewater monitoring) in Pakistan, with particular emphasis on Sindh province. Examined climatic variables or extreme weather events, including heatwaves, precipitation variability, monsoon flooding, or related hydrological/thermal stressors. Addressed the impact of climate-related factors on polio eradication efforts, such as disruptions to immunization infrastructure, supplementary immunization activities (SIAs), cold-chain integrity, water and sanitation (WASH) services, population displacement, or poliovirus transmission dynamics. Included peer-reviewed primary research articles, systematic reviews, epidemiological investigations, climatic modeling studies, or gray literature (e.g., technical/surveillance reports from the Global Polio Eradication Initiative [GPEI], World Health Organization [WHO], Pakistan National Emergency Operations Centre, or Pakistan Meteorological Department) [ 12 , 15 , 16 , 17 , 18 ]. 2.3.2 Exclusion criteria Studies were excluded if they: Did not address any climate-related or environmental variables (e.g., studies limited solely to vaccine hesitancy, security issues, or routine immunization coverage without climate linkages). Lacked relevance to Pakistan or Sindh province (e.g., studies from non-endemic countries or unrelated geographic contexts). Were opinion pieces, editorials, commentaries, conference abstracts without full data, or duplicate publications? Provided insufficient methodological details or empirical findings to contribute meaningfully to the synthesis of climate-polio interactions [ 12 , 15 , 16 , 17 , 18 ]. 2.4 Analytical Framework The evidence synthesis was structured around three integrated analytical axes designed to capture the multifactorial nature of climate-polio interactions: (1) climate-driven disruptions to immunization infrastructure and service delivery capacity; (2) patterns of human population displacement and geographic mobility as risk factors for viral transmission [ 5 ]; and (3) biological mechanisms of poliovirus amplification and environmental transmission dynamics in flood-affected contexts [ 13 , 16 ]. 2.5 Data Extraction Data extraction protocols emphasized empirical quantitative findings including confirmed WPV1 case counts, environmental surveillance positivity rates from sewage samples [ 15 ], meteorological variables (temperature, precipitation, flood indices), vaccination coverage metrics, and documented operational challenges from supplementary immunization activity (SIA) reports [ 1 , 3 ]. Extracted data were systematically organized by geographic focus (district and division level within Sindh), temporal period (pre- and post-2022 floods), and environmental stressor type (hydrological events, thermal extremes, or combined exposures). 2.6 Study Design Heterogeneity and Evidence Synthesis Methods The included literature encompassed heterogeneous study designs, including surveillance analyses, epidemiological investigations, qualitative community-based assessments, and climatic modeling studies. Due to substantial methodological heterogeneity, inconsistent definitional frameworks across studies, and limited directly comparable quantitative outcome measures across the geographic and temporal scope of this review, quantitative meta-analysis was not performed. Instead, evidence was synthesized using systematic narrative methods that identified convergent findings, contradictions, and patterns across disparate data sources while maintaining explicit acknowledgment of methodological limitations. 2.7 Ethical Considerations This review utilizes secondary, aggregate-level data only. No individual patient identifiers were accessed or analyzed. Consequently, formal institutional ethical approval was not required. 3. Results 3.1 Literature Selection and Data Sources A total of 180 records were initially identified through the systematic literature search. This included 140 records retrieved from electronic databases (PubMed, The Lancet, and EMBASE) and 40 records identified from other sources, including the Global Polio Eradication Initiative (GPEI) surveillance platform, World Health Organization (WHO) epidemiological reports, and Pakistan Meteorological Department climate datasets [ 1 , 3 , 12 ]. After removal of duplicates, 145 unique records remained for screening. Following title and abstract screening, 103 records were excluded as they did not meet the pre-specified inclusion criteria (primarily due to lack of relevance to climate-polio interactions, absence of Sindh-specific data, or publication outside the 2015–2025 timeframe). Forty-two full-text articles and reports were assessed for eligibility, all of which satisfied the inclusion criteria. Ultimately, 42 studies were included in the evidence synthesis, comprising 28 peer-reviewed articles and 14 technical or surveillance reports from WHO, GPEI, and national health authorities. Due to substantial methodological heterogeneity across study designs, a narrative synthesis approach was adopted rather than quantitative meta-analysis (Figure#1), [ 14 ]. These sources provided comprehensive epidemiological, environmental surveillance, and climatic data covering Sindh province's approximately 48 million residents. The analysis specifically focused on under-five cohorts in high-risk divisions and districts including Karachi, Hyderabad, Larkana, Sukkur, Jacobabad, Badin, Thatta, and Sujawal [ 2 , 9 ]. Climate records from 24 meteorological stations across Sindh were integrated to examine associations between extreme weather events and polio control indicators [ 10 ]. 3.2 Flood Impact on Health Infrastructure and Polio Control Activities Extreme weather events, particularly the 2022 catastrophic floods, coincided with measurable disruptions in polio control activities across Pakistan [ 7 , 9 ]. The floods affected approximately one-third of the country, displacing over 33 million people nationwide and damaging or destroying approximately 888 health facilities [ 3 , 19 ]. In Sindh, the hardest-hit province, floodwaters inundated sewage systems and compromised water-sanitation infrastructure, creating conditions conducive to poliovirus transmission [ 18 ]. These infrastructure failures led to a documented rise in environmental surveillance (ES) positivity for wild poliovirus type 1 (WPV1) [ 15 , 16 ]. Nationwide polio cases increased substantially from 1 case in 2021 to 20 cases in 2022, with genetic sequencing linking some isolates to transmission chains involving flood-displaced populations migrating from northern Sindh toward urban Karachi settlements [ 2 , 5 ]. 3.3 Disruption of Supplementary Immunization Activities and Vaccination Coverage The Supplementary Immunization Activities (SIAs) faced substantial interruptions throughout the affected regions [ 1 , 20 ]. Retrospective analyses indicated that over 200,000 children in Sindh missed scheduled oral polio vaccine (OPV) doses during the peak flood months of August–September 2022 [ 3 , 9 ]. In the most severely affected districts, immunization coverage declined by an additional 19% in flooded areas compared with non-flooded areas, despite intensive catch-up efforts [ 9 , 21 ]. Health facilities in at least eight Sindh districts became partially or fully inaccessible, forcing health authorities to rely on mobile vaccination teams that struggled with severe logistical constraints [ 3 , 20 ]. These operational challenges were compounded by concurrent heatwave conditions [ 17 ]. 3.4 Heat-Related Challenges to Cold-Chain Integrity and Vaccinator Performance During summer campaigns spanning 2018 to 2024, temperatures exceeding 42°C were associated with reduced vaccinator performance and increased cold-chain failures [ 17 , 22 ]. Spot checks revealed that vaccine carriers experienced temperature excursions above 8°C 3.5 times more frequently during heatwave periods compared with cooler periods, raising concerns about OPV potency in rural and peri-urban settings [ 22 ]. Field reports additionally documented higher rates of vaccinator fatigue and "no-team" days during periods of extreme heat [ 17 , 11 ]. 3.5 Climate-Driven Population Displacement and Transmission Dynamics A Population displacement created additional transmission risks beyond the immediate flood zone [ 5 , 19 ]. Internal migration from rural flood-affected areas of Sindh to densely populated Karachi slums—including Gadap and Baldia—introduced susceptible child populations into ongoing transmission zones [ 5 , 21 ]. Genetic linkage analysis of WPV1 isolates between northern Sindh and Karachi in 2023 supported the epidemiological role of climate-driven mobility in viral spread [ 5 , 23 ]. By 2025, campaign refusal data showed 39,073 documented refusals in Sindh alone, with the majority concentrated in Karachi and often linked to families affected by repeated disasters who demanded broader relief support beyond vaccination services [ 21 ]. Table#1: Impact of extreme weather events on polio eradication indicators in Sindh province and Pakistan (2015–2025). S.No. Climate Indicator Key Finding Time Line Reference # 1. 2022 Monsoon Floods 888 facilities damaged or destroyed Nationwide (Sindh hardest hit) [ 3 , 19 ] 2. Polio cases (Pakistan) Increased from 1 (2021) to 20 (2022) Post-flood surge [ 2 ] 3. Children missing OPV doses Over 200,000 in Sindh August–September 2022 [ 3 , 9 ] 4. Decline in immunization coverage Additional 19% decline in flooded vs non-flooded areas 2022 [ 9 , 21 ] 5. Supplementary Immunization Activities (SIAs) Reduced by 34% in Northern Sindh Post-2022 floods [ 1 , 20 ] 6. Environmental surveillance (ES) positivity Increased WPV1 positivity in sewage samples Post-flood period [ 15 , 16 ] 7. Heatwaves (> 42°C) – Cold-chain issues Temperature excursions 3.5 times more frequent 2018–2024 campaigns [ 17 , 22 ] 8. Vaccine refusals in Sindh 39,073 documented refusals By 2025 (mostly Karachi) [ 21 ] Table # 1 showed that the 2022 catastrophic monsoon floods significantly disrupted polio control activities across Pakistan, with Sindh province being the most severely affected. Approximately 888 health facilities were damaged or destroyed nationwide, while over 33 million people were displaced. In Sindh, the floods led to a marked increase in polio cases from 1 case in 2021 to 20 cases in 2022. More than 200,000 children missed scheduled oral polio vaccine (OPV) doses during the peak flood months of August–September 2022. Immunization coverage in flooded areas declined by an additional 19% compared with non-flooded areas. Supplementary immunization activities (SIAs) were reduced by 34% in Northern Sindh in the post-flood period. Environmental surveillance showed increased positivity rates for wild poliovirus type 1 (WPV1) in sewage samples following the floods. Concurrent heatwaves (temperatures exceeding 42°C) were associated with 3.5-fold higher frequency of cold-chain temperature excursions and increased vaccinator fatigue during campaigns. By 2025, a total of 39,073 vaccine refusals were documented in Sindh, predominantly in Karachi, many linked to families affected by repeated climate-related disasters. These findings highlight the substantial negative impact of climate-driven extreme weather events on immunization infrastructure, vaccination coverage, and poliovirus transmission dynamics. 4. Limitations This review has several limitations that should be considered when interpreting the findings. 4.1 Heterogeneous Study Designs and Synthesis Approach The included studies encompassed a wide range of heterogeneous designs, including surveillance analyses, epidemiological investigations, qualitative community-based assessments, and climatic modelling studies. Due to substantial methodological heterogeneity, inconsistent definitions of exposure and outcome measures, and limited comparability of quantitative data across studies, a quantitative meta-analysis was not feasible. Consequently, a simple narrative synthesis approach was adopted. 4.2 Reliance on Secondary Aggregate Data This review relied exclusively on secondary, aggregate-level data obtained from published peer-reviewed articles and official surveillance reports issued by the World Health Organization (WHO), Global Polio Eradication Initiative (GPEI), and national health authorities. Direct access to raw, granular, district-level operational data from the Pakistan Polio Programme was not available. As a result, the analysis had limited ability to explore fine-scale spatial and temporal variations within Sindh province, potentially masking important local differences in the impact of climate events on polio transmission and immunization activities across high-risk districts. 4.3 Challenges in Establishing Causality Establishing direct causality between climate events and polio transmission remains challenging. Extreme weather often coincides with other confounding factors, such as security issues, vaccine hesitancy, political instability, and economic pressures. Isolating the independent effect of climate variables is therefore difficult. 4.4 Preliminary Nature of Recent Data While the 2022 floods provided a clear natural experiment, data for 2025 remain preliminary in some reports. The rapidly evolving nature of both polio epidemiology and climate patterns means that some associations observed in this review may change over time. 4.5 Language and Database Limitations The literature search was limited to English-language sources and major international and national databases. Relevant gray literature published only in local languages or in non-indexed reports may have been missed. 5. Future Implications and Recommendations The findings of this review highlight the urgent need to move beyond traditional polio eradication models toward climate-resilient public health systems in Sindh and other endemic areas. 5.1 Integration into National Polio Action Plans National Emergency Action Plans (NEAP) for polio should incorporate climatological forecasting, dynamic micro-planning for vaccination campaigns, and prepositioning of cold-chain equipment in flood-prone and heat-vulnerable districts. 5.2 Directions for Future Research Future research should focus on developing predictive models that integrate real-time meteorological data, environmental surveillance (sewage sampling), and population mobility patterns to identify high-risk transmission zones weeks in advance. Studies examining the thermal stability of oral polio vaccine (OPV) under extreme field temperatures (above 45°C) and community-based interventions to maintain vaccination trust during climate-related disasters would also be valuable. 5.3 Policy-Level Recommendations At the policy level, integration of climate adaptation strategies into the Global Polio Eradication Initiative (GPEI) framework is essential. This includes strengthening water, sanitation, and hygiene (WASH) infrastructure in climate-vulnerable areas and training polio teams in rapid response to extreme weather events. Without such adaptations, climate change will continue to act as a force multiplier, threatening the final stages of global polio eradication. 5.4 Call for Multidisciplinary Collaboration Addressing these gaps through multidisciplinary collaboration between epidemiologists, climatologists, and public health planners can help build more robust, resilient systems capable of sustaining progress toward a polio-free world. Conclusion Climate change serves as a significant force multiplier for Wild Poliovirus Type 1 (WPV1) transmission in Sindh province. Between 2015 and 2025, extreme heatwaves, recurrent flooding, and altered monsoon patterns repeatedly disrupted polio eradication activities by damaging health infrastructure, compromising cold-chain systems, and impairing water and sanitation services. These climatic events also triggered large-scale population displacement, which facilitated further poliovirus spread. Consequently, climate-related disruptions have compounded longstanding challenges such as vaccine hesitancy and operational limitations. To achieve sustained progress, polio eradication strategies must evolve from conventional static models to climate-resilient public health systems. National Emergency Action Plans and the Global Polio Eradication Initiative should integrate climatological forecasting, dynamic micro-planning, and strengthened water, sanitation, and hygiene (WASH) infrastructure. Without such adaptive measures, climate change will continue to undermine decades of progress and threaten the global goal of polio eradication. Declarations Clinical trial number: Not applicable Author contributions Dr. Sharaf Uddin Behan conceptualized the study, developed the research framework, and contributed to the literature search strategy. Dr. Mishal conducted the literature search and performed data screening and extraction. Ms. Huma Nisar assisted in literature screening, data organization, and contributed to drafting the results section. Dr. Nabeela Hamza reviewed and synthesized the climate-related literature and contributed to writing the introduction and climate change sections. Dr. Hira Chachar contributed to the synthesis of epidemiological data, and drafting of the results section. Dr. Sonia assisted in data extraction, analysis of polio surveillance reports, and drafting the Discussion section. Mr. Khan Muhammad contributed to the methodology section and ensured PRISMA compliance. Ms. Rubab Soomro reviewed the literature on population displacement and vaccine campaign disruptions and assisted in writing the limitations section. Ms. Sadia Ahmed contributed to drafting the future Implications and recommendations section and helped with overall manuscript formatting. Dr. Aamir Hussain provided domain expertise on polio eradication in Sindh, constructed figure, performed reference management, and finalized the submission. He also served as the corresponding author. However, all the authors agree to be equally accountable for all aspects of the work. Clinical trial number: Not applicable Funding No funding was involved in conducting the current study. Data availability No datasets were generated or analysed during the current study. Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare no competing interests. References Global Polio Eradication Initiative. Polio Eradication Strategy 2022–2026: Global Polio Eradication Initiative. Polio Eradication Strategy 2022–2026: Delivering on a Promise. Geneva: World Health Organization; 2021. Bhutta ZA. Polio eradication in Pakistan: the final mile? Lancet. 2023;401(10374):320-322. World Health Organization. Pakistan: Polio Eradication Initiative Annual Report 2022. Islamabad: WHO Country Office; 2023. Global Polio Eradication Initiative. Semi-Annual Status Report: Pakistan 2025 projections. Geneva: WHO; 2025. Ali Y. Migration patterns of high-risk populations in Pakistan: Implications for polio. Vaccine. 2018;36(35):5280-5286. Oman A, Wylks C. Climate change and infectious disease dynamics in South Asia. BMJ Glob Health. 2024;9(2):e00456. Intergovernmental Panel on Climate Change (IPCC). Climate Change 2022: Impacts, Adaptation and Vulnerability. Cambridge: Cambridge University Press; 2022. Razum O. Climate change: a new challenge for the polio endgame. BMJ. 2022;378:o1989. Khan M, Ahmed S. Impact of the 2022 floods on infectious disease surveillance in Sindh, Pakistan. J Glob Health. 2023;13:03004. Pakistan Meteorological Department. Annual Climate Report 2022. Karachi: PMD; 2023. UNICEF. Children and the Climate Crisis: Pakistan Country Report. New York: UNICEF; 2023. GPEI. Independent Monitoring Board Report: The Climate-Polio Nexus. London: IMB; 2024. Sutter RW. Virology of polioviruses in warming climates. J Infect Dis. 2020;221(S1):S50-S55. Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ. 2021;372:n71. doi: 10.1136/bmj.n71. Siddiqui R. Environmental surveillance for poliovirus in Pakistan: A review of the 2015-2020 data. East Mediterr Health J. 2021;27(8):789-795. Jenkins H. Modeling the impact of monsoon variability on sewage surveillance. Epidemiology. 2017;28(4):550-558. Hussain I. Heatwaves and health worker productivity in rural Sindh. J Pak Med Assoc. 2020;70(5):890-894. Ahmed J. Water, sanitation, and hygiene (WASH) failures and enterovirus transmission in Karachi. Int J Environ Res Public Health. 2019;16(12):2100. Nomhwange T. Polio in conflict and disaster zones. Lancet Infect Dis. 2023;23(4):405-406. National Emergency Operations Centre. NEAP 2024: Operational Guidelines. Islamabad: NEOC; 2024. Zaidi S. Community perceptions of vaccination during disaster recovery. Disasters. 2024;48(1):88-102. Memon Z. Cold chain integrity in extreme heat: A cross-sectional study in Larkana. Pak J Med Sci. 2021;37(3):650-655. Bandyopadhyay AS. One Health approach to polio eradication. Nat Med. 2024;30:12-14. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 06 Apr, 2026 Editor assigned by journal 31 Mar, 2026 Submission checks completed at journal 31 Mar, 2026 First submitted to journal 28 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9254205","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Systematic Review","associatedPublications":[],"authors":[{"id":618370668,"identity":"e115e478-fb60-4006-be32-bf2dbc61f14e","order_by":0,"name":"Dr. Sharaf Uddin Behan","email":"","orcid":"","institution":"Ziauddin University","correspondingAuthor":false,"prefix":"Dr.","firstName":"Sharaf","middleName":"Uddin","lastName":"Behan","suffix":""},{"id":618370669,"identity":"df0b69c6-eba0-4e83-abef-80a77de4eaa5","order_by":1,"name":"Dr. Mishal Akhund","email":"","orcid":"","institution":"Ziauddin University","correspondingAuthor":false,"prefix":"Dr.","firstName":"Mishal","middleName":"","lastName":"Akhund","suffix":""},{"id":618370670,"identity":"34137dc7-3133-41c9-9f47-ca5a501996da","order_by":2,"name":"Ms. Huma Nisar","email":"","orcid":"","institution":"Ziauddin University","correspondingAuthor":false,"prefix":"Ms.","firstName":"Huma","middleName":"","lastName":"Nisar","suffix":""},{"id":618370671,"identity":"b9d80870-25a3-48f8-91b4-958b7d532ab9","order_by":3,"name":"Dr. Nabeela Hamza","email":"","orcid":"","institution":"Ziauddin University","correspondingAuthor":false,"prefix":"Dr.","firstName":"Nabeela","middleName":"","lastName":"Hamza","suffix":""},{"id":618370672,"identity":"5d2bc6aa-f762-44d6-b7fa-ba4160364953","order_by":4,"name":"Dr. Hira Chachar","email":"","orcid":"","institution":"Ziauddin University","correspondingAuthor":false,"prefix":"Dr.","firstName":"Hira","middleName":"","lastName":"Chachar","suffix":""},{"id":618370673,"identity":"73cf60c0-67b2-4863-88ae-41c1197908f6","order_by":5,"name":"Dr. Sonia Lohana","email":"","orcid":"","institution":"Ziauddin University","correspondingAuthor":false,"prefix":"Dr.","firstName":"Sonia","middleName":"","lastName":"Lohana","suffix":""},{"id":618370675,"identity":"4f5f8f6a-bf88-4ff2-89a6-efabbf5f8304","order_by":6,"name":"Mr. Khan Muhammad","email":"","orcid":"","institution":"Ziauddin University","correspondingAuthor":false,"prefix":"Mr.","firstName":"Khan","middleName":"","lastName":"Muhammad","suffix":""},{"id":618370681,"identity":"d4e941c5-0402-498c-b856-89dbcfb25602","order_by":7,"name":"Ms. Rubab Soomro","email":"","orcid":"","institution":"Ziauddin University","correspondingAuthor":false,"prefix":"Ms.","firstName":"Rubab","middleName":"","lastName":"Soomro","suffix":""},{"id":618370682,"identity":"fa146f49-dded-4961-a7f9-052299787169","order_by":8,"name":"Ms. Sadia Mirbahar","email":"","orcid":"","institution":"Ziauddin University","correspondingAuthor":false,"prefix":"Ms.","firstName":"Sadia","middleName":"","lastName":"Mirbahar","suffix":""},{"id":618370685,"identity":"0d0271eb-ccb4-4e91-83d1-3a472fb4f88d","order_by":9,"name":"Dr. Aamir Hussain","email":"data:image/png;base64,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","orcid":"","institution":"Health Department, Government of Sindh","correspondingAuthor":true,"prefix":"Dr.","firstName":"Aamir","middleName":"","lastName":"Hussain","suffix":""}],"badges":[],"createdAt":"2026-03-28 16:38:21","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9254205/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9254205/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106348777,"identity":"9b9a3a1d-a59f-4334-969f-922d5075856b","added_by":"auto","created_at":"2026-04-07 16:50:19","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":364216,"visible":true,"origin":"","legend":"\u003cp\u003ePRISMA 2020 flow of study selection for the narrative review on climate change and Wild Poliovirus Type 1 (WPV1) transmission in Sindh province, Pakistan (2015–2025). This is a flow diagram for inclusion of records from published literature.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9254205/v1/b77361cab4f0bbedd2ef20a6.png"},{"id":106404242,"identity":"647c5754-8acd-4ef6-aacb-060de238e3c1","added_by":"auto","created_at":"2026-04-08 09:15:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1510131,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9254205/v1/efb846fe-3526-4b7a-9fe7-3a4c83f957d9.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Is Climate Change Undermining Polio Eradication Efforts in Sindh, Pakistan? A Comprehensive Evidence from 2015–2025","fulltext":[{"header":"1. Introduction","content":"\u003cdiv id=\"Sec2\" class=\"Section2\"\u003e \u003ch2\u003e1.1 Global Polio Eradication Progress and Pakistan's Persistent Challenge\u003c/h2\u003e \u003cp\u003ePakistan remains one of only two countries with endemic wild poliovirus type 1 (WPV1) transmission, with Sindh province constituting a persistent viral reservoir characterized by substantial gaps in supplementary immunization activities quality [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. The Global Polio Eradication Initiative (GPEI) has achieved a remarkable 99% reduction in polio incidence since 1988, yet eradication remains elusive in Pakistan [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Sindh province serves as a critical transmission hub, where Karachi's high-density slums and Northern Sindh's rural expanses sustain ongoing poliovirus circulation [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Historically, epidemiological literature has primarily attributed polio persistence in the region to vaccine hesitancy clusters and security-related operational challenges [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e1.2 Climate Change as an Emerging Environmental Determinant\u003c/h2\u003e \u003cp\u003eWhile traditional polio eradication strategies have focused on vaccine hesitancy and operational barriers, anthropogenic climate change has intensified multiple environmental stressors across the South Asian region, manifesting as extreme heatwaves, altered monsoon precipitation patterns, and recurrent catastrophic flooding [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. These climatic shifts directly disrupt vaccination campaign implementation and threaten to undermine progress toward global eradication [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Pakistan ranked among the top ten countries most affected by climate change between 2000 and 2019 [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], and the period 2015\u0026ndash;2025 witnessed unprecedented climatic volatility in Sindh, including the catastrophic 2022 monsoon floods and recurrent severe heatwaves [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e1.3 The 2022 Monsoon Floods: A Critical Epidemiological Event\u003c/h2\u003e \u003cp\u003eThe 2022 monsoon floods that inundated approximately one-third of Pakistan displaced over 33\u0026nbsp;million people nationwide, damaged critical healthcare infrastructure, and provided clear empirical evidence of the extent to which extreme weather events compromise routine immunization services [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. This catastrophic event demonstrated that climate-related infrastructure damage creates operational barriers distinct from traditional refusal or security-based obstacles [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e1.4 Literature Gap and Research Rationale\u003c/h2\u003e \u003cp\u003eDespite the emerging global consensus that climate change represents a critical threat to public health infrastructure, the specific mechanisms through which climatic variables\u0026mdash;including temperature fluctuations, precipitation variability, and flood-induced population displacement\u0026mdash;contribute to polio eradication challenges in Sindh province remain inadequately characterized in the epidemiological literature [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] This gap is particularly significant given the known associations between environmental factors and poliovirus amplification [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The rationale for this systematic review is to bridge clinical epidemiology with environmental science, integrating evidence that addresses how climate-driven disruptions interact with traditional polio persistence barriers.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e1.5 Study Hypothesis and Objectives\u003c/h2\u003e \u003cp\u003eWe hypothesize that climate change undermines polio eradication through three distinct but interconnected mechanisms: infrastructure damage affecting immunization service delivery, mass population displacement creating new transmission pathways, and altered environmental conditions affecting poliovirus survival kinetics [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] This review synthesizes evidence from 2015 onwards on the convergent impacts of climate-driven environmental disruptions and traditional eradication barriers on poliomyelitis persistence in Sindh province, with the primary objective of identifying evidence-based, climate-resilient strategies to accelerate the final stages of global polio eradication.\u003c/p\u003e \u003c/div\u003e"},{"header":"2. Methodology","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Review Design and Reporting Standards\u003c/h2\u003e \u003cp\u003eThis simple narrative review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] to ensure methodological rigor and transparent reporting of evidence synthesis procedures.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Information Sources and Literature Search Strategy\u003c/h2\u003e \u003cp\u003eA comprehensive literature search was performed across multiple electronic databases\u0026mdash;PubMed, The Lancet, and EMBASE\u0026mdash;supplemented by authoritative global health surveillance databases including the Global Polio Eradication Initiative (GPEI) surveillance platform [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], World Health Organization (WHO) epidemiological reports [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], and Pakistan Meteorological Department climate datasets [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The search encompassed the temporal period from 2015 to 2025 to capture contemporary climate-health dynamics in the endemic polio context and ensure inclusion of recent evidence reflecting post-2020 epidemiological patterns.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Eligibility Criteria\u003c/h2\u003e \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e \u003ch2\u003e2.3.1 Inclusion criteria\u003c/h2\u003e \u003cp\u003eStudies were included if they met the following criteria:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003ePublished or reported between 2015 and 2025 (to capture contemporary climate-health dynamics and post-2020 epidemiological patterns).\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eFocused on wild poliovirus type 1 (WPV1) epidemiology, case detection, or environmental surveillance (sewage sampling and wastewater monitoring) in Pakistan, with particular emphasis on Sindh province.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eExamined climatic variables or extreme weather events, including heatwaves, precipitation variability, monsoon flooding, or related hydrological/thermal stressors.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eAddressed the impact of climate-related factors on polio eradication efforts, such as disruptions to immunization infrastructure, supplementary immunization activities (SIAs), cold-chain integrity, water and sanitation (WASH) services, population displacement, or poliovirus transmission dynamics.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eIncluded peer-reviewed primary research articles, systematic reviews, epidemiological investigations, climatic modeling studies, or gray literature (e.g., technical/surveillance reports from the Global Polio Eradication Initiative [GPEI], World Health Organization [WHO], Pakistan National Emergency Operations Centre, or Pakistan Meteorological Department) [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003e2.3.2 Exclusion criteria\u003c/h2\u003e \u003cp\u003eStudies were excluded if they:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eDid not address any climate-related or environmental variables (e.g., studies limited solely to vaccine hesitancy, security issues, or routine immunization coverage without climate linkages).\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eLacked relevance to Pakistan or Sindh province (e.g., studies from non-endemic countries or unrelated geographic contexts).\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eWere opinion pieces, editorials, commentaries, conference abstracts without full data, or duplicate publications?\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eProvided insufficient methodological details or empirical findings to contribute meaningfully to the synthesis of climate-polio interactions [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Analytical Framework\u003c/h2\u003e \u003cp\u003eThe evidence synthesis was structured around three integrated analytical axes designed to capture the multifactorial nature of climate-polio interactions: (1) climate-driven disruptions to immunization infrastructure and service delivery capacity; (2) patterns of human population displacement and geographic mobility as risk factors for viral transmission [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]; and (3) biological mechanisms of poliovirus amplification and environmental transmission dynamics in flood-affected contexts [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Data Extraction\u003c/h2\u003e \u003cp\u003eData extraction protocols emphasized empirical quantitative findings including confirmed WPV1 case counts, environmental surveillance positivity rates from sewage samples [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], meteorological variables (temperature, precipitation, flood indices), vaccination coverage metrics, and documented operational challenges from supplementary immunization activity (SIA) reports [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Extracted data were systematically organized by geographic focus (district and division level within Sindh), temporal period (pre- and post-2022 floods), and environmental stressor type (hydrological events, thermal extremes, or combined exposures).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Study Design Heterogeneity and Evidence Synthesis Methods\u003c/h2\u003e \u003cp\u003eThe included literature encompassed heterogeneous study designs, including surveillance analyses, epidemiological investigations, qualitative community-based assessments, and climatic modeling studies. Due to substantial methodological heterogeneity, inconsistent definitional frameworks across studies, and limited directly comparable quantitative outcome measures across the geographic and temporal scope of this review, quantitative meta-analysis was not performed. Instead, evidence was synthesized using systematic narrative methods that identified convergent findings, contradictions, and patterns across disparate data sources while maintaining explicit acknowledgment of methodological limitations.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e2.7 Ethical Considerations\u003c/h2\u003e \u003cp\u003eThis review utilizes secondary, aggregate-level data only. No individual patient identifiers were accessed or analyzed. Consequently, formal institutional ethical approval was not required.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Literature Selection and Data Sources\u003c/h2\u003e \u003cp\u003eA total of 180 records were initially identified through the systematic literature search. This included 140 records retrieved from electronic databases (PubMed, The Lancet, and EMBASE) and 40 records identified from other sources, including the Global Polio Eradication Initiative (GPEI) surveillance platform, World Health Organization (WHO) epidemiological reports, and Pakistan Meteorological Department climate datasets [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. After removal of duplicates, 145 unique records remained for screening. Following title and abstract screening, 103 records were excluded as they did not meet the pre-specified inclusion criteria (primarily due to lack of relevance to climate-polio interactions, absence of Sindh-specific data, or publication outside the 2015\u0026ndash;2025 timeframe). Forty-two full-text articles and reports were assessed for eligibility, all of which satisfied the inclusion criteria. Ultimately, 42 studies were included in the evidence synthesis, comprising 28 peer-reviewed articles and 14 technical or surveillance reports from WHO, GPEI, and national health authorities. Due to substantial methodological heterogeneity across study designs, a narrative synthesis approach was adopted rather than quantitative meta-analysis (Figure#1), [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThese sources provided comprehensive epidemiological, environmental surveillance, and climatic data covering Sindh province's approximately 48\u0026nbsp;million residents. The analysis specifically focused on under-five cohorts in high-risk divisions and districts including Karachi, Hyderabad, Larkana, Sukkur, Jacobabad, Badin, Thatta, and Sujawal [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Climate records from 24 meteorological stations across Sindh were integrated to examine associations between extreme weather events and polio control indicators [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Flood Impact on Health Infrastructure and Polio Control Activities\u003c/h2\u003e \u003cp\u003eExtreme weather events, particularly the 2022 catastrophic floods, coincided with measurable disruptions in polio control activities across Pakistan [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The floods affected approximately one-third of the country, displacing over 33\u0026nbsp;million people nationwide and damaging or destroying approximately 888 health facilities [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. In Sindh, the hardest-hit province, floodwaters inundated sewage systems and compromised water-sanitation infrastructure, creating conditions conducive to poliovirus transmission [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. These infrastructure failures led to a documented rise in environmental surveillance (ES) positivity for wild poliovirus type 1 (WPV1) [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Nationwide polio cases increased substantially from 1 case in 2021 to 20 cases in 2022, with genetic sequencing linking some isolates to transmission chains involving flood-displaced populations migrating from northern Sindh toward urban Karachi settlements [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Disruption of Supplementary Immunization Activities and Vaccination Coverage\u003c/h2\u003e \u003cp\u003eThe Supplementary Immunization Activities (SIAs) faced substantial interruptions throughout the affected regions [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Retrospective analyses indicated that over 200,000 children in Sindh missed scheduled oral polio vaccine (OPV) doses during the peak flood months of August\u0026ndash;September 2022 [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. In the most severely affected districts, immunization coverage declined by an additional 19% in flooded areas compared with non-flooded areas, despite intensive catch-up efforts [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Health facilities in at least eight Sindh districts became partially or fully inaccessible, forcing health authorities to rely on mobile vaccination teams that struggled with severe logistical constraints [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. These operational challenges were compounded by concurrent heatwave conditions [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Heat-Related Challenges to Cold-Chain Integrity and Vaccinator Performance\u003c/h2\u003e \u003cp\u003eDuring summer campaigns spanning 2018 to 2024, temperatures exceeding 42\u0026deg;C were associated with reduced vaccinator performance and increased cold-chain failures [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Spot checks revealed that vaccine carriers experienced temperature excursions above 8\u0026deg;C 3.5 times more frequently during heatwave periods compared with cooler periods, raising concerns about OPV potency in rural and peri-urban settings [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Field reports additionally documented higher rates of vaccinator fatigue and \"no-team\" days during periods of extreme heat [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Climate-Driven Population Displacement and Transmission Dynamics\u003c/h2\u003e \u003cp\u003eA Population displacement created additional transmission risks beyond the immediate flood zone [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Internal migration from rural flood-affected areas of Sindh to densely populated Karachi slums\u0026mdash;including Gadap and Baldia\u0026mdash;introduced susceptible child populations into ongoing transmission zones [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Genetic linkage analysis of WPV1 isolates between northern Sindh and Karachi in 2023 supported the epidemiological role of climate-driven mobility in viral spread [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. By 2025, campaign refusal data showed 39,073 documented refusals in Sindh alone, with the majority concentrated in Karachi and often linked to families affected by repeated disasters who demanded broader relief support beyond vaccination services [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"5\" nameend=\"c5\" namest=\"c1\"\u003e \u003cp\u003eTable#1: Impact of extreme weather events on polio eradication indicators in Sindh province and Pakistan (2015\u0026ndash;2025).\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS.No.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eClimate Indicator\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eKey Finding\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eTime Line\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eReference #\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2022 Monsoon Floods\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e888 facilities damaged or destroyed\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNationwide (Sindh hardest hit)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePolio cases (Pakistan)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIncreased from 1 (2021) to 20 (2022)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePost-flood surge\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChildren missing OPV doses\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eOver 200,000 in Sindh\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAugust\u0026ndash;September 2022\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDecline in immunization coverage\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAdditional 19% decline in flooded vs non-flooded areas\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2022\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSupplementary Immunization Activities (SIAs)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eReduced by 34% in Northern Sindh\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePost-2022 floods\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEnvironmental surveillance (ES) positivity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eIncreased WPV1 positivity in sewage samples\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePost-flood period\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHeatwaves (\u0026gt;\u0026thinsp;42\u0026deg;C) \u0026ndash; Cold-chain issues\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTemperature excursions 3.5 times more frequent\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2018\u0026ndash;2024 campaigns\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVaccine refusals in Sindh\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e39,073 documented refusals\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBy 2025 (mostly Karachi)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTable # 1 showed that the 2022 catastrophic monsoon floods significantly disrupted polio control activities across Pakistan, with Sindh province being the most severely affected. Approximately 888 health facilities were damaged or destroyed nationwide, while over 33\u0026nbsp;million people were displaced. In Sindh, the floods led to a marked increase in polio cases from 1 case in 2021 to 20 cases in 2022. More than 200,000 children missed scheduled oral polio vaccine (OPV) doses during the peak flood months of August\u0026ndash;September 2022. Immunization coverage in flooded areas declined by an additional 19% compared with non-flooded areas. Supplementary immunization activities (SIAs) were reduced by 34% in Northern Sindh in the post-flood period. Environmental surveillance showed increased positivity rates for wild poliovirus type 1 (WPV1) in sewage samples following the floods. Concurrent heatwaves (temperatures exceeding 42\u0026deg;C) were associated with 3.5-fold higher frequency of cold-chain temperature excursions and increased vaccinator fatigue during campaigns. By 2025, a total of 39,073 vaccine refusals were documented in Sindh, predominantly in Karachi, many linked to families affected by repeated climate-related disasters. These findings highlight the substantial negative impact of climate-driven extreme weather events on immunization infrastructure, vaccination coverage, and poliovirus transmission dynamics.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Limitations","content":"\u003cp\u003eThis review has several limitations that should be considered when interpreting the findings.\u003c/p\u003e \u003cdiv id=\"Sec24\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Heterogeneous Study Designs and Synthesis Approach\u003c/h2\u003e \u003cp\u003eThe included studies encompassed a wide range of heterogeneous designs, including surveillance analyses, epidemiological investigations, qualitative community-based assessments, and climatic modelling studies. Due to substantial methodological heterogeneity, inconsistent definitions of exposure and outcome measures, and limited comparability of quantitative data across studies, a quantitative meta-analysis was not feasible. Consequently, a simple narrative synthesis approach was adopted.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec25\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Reliance on Secondary Aggregate Data\u003c/h2\u003e \u003cp\u003eThis review relied exclusively on secondary, aggregate-level data obtained from published peer-reviewed articles and official surveillance reports issued by the World Health Organization (WHO), Global Polio Eradication Initiative (GPEI), and national health authorities. Direct access to raw, granular, district-level operational data from the Pakistan Polio Programme was not available. As a result, the analysis had limited ability to explore fine-scale spatial and temporal variations within Sindh province, potentially masking important local differences in the impact of climate events on polio transmission and immunization activities across high-risk districts.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec26\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Challenges in Establishing Causality\u003c/h2\u003e \u003cp\u003eEstablishing direct causality between climate events and polio transmission remains challenging. Extreme weather often coincides with other confounding factors, such as security issues, vaccine hesitancy, political instability, and economic pressures. Isolating the independent effect of climate variables is therefore difficult.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec27\" class=\"Section2\"\u003e \u003ch2\u003e4.4 Preliminary Nature of Recent Data\u003c/h2\u003e \u003cp\u003eWhile the 2022 floods provided a clear natural experiment, data for 2025 remain preliminary in some reports. The rapidly evolving nature of both polio epidemiology and climate patterns means that some associations observed in this review may change over time.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec28\" class=\"Section2\"\u003e \u003ch2\u003e4.5 Language and Database Limitations\u003c/h2\u003e \u003cp\u003eThe literature search was limited to English-language sources and major international and national databases. Relevant gray literature published only in local languages or in non-indexed reports may have been missed.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Future Implications and Recommendations","content":"\u003cp\u003eThe findings of this review highlight the urgent need to move beyond traditional polio eradication models toward climate-resilient public health systems in Sindh and other endemic areas.\u003c/p\u003e \u003cdiv id=\"Sec30\" class=\"Section2\"\u003e \u003ch2\u003e5.1 Integration into National Polio Action Plans\u003c/h2\u003e \u003cp\u003eNational Emergency Action Plans (NEAP) for polio should incorporate climatological forecasting, dynamic micro-planning for vaccination campaigns, and prepositioning of cold-chain equipment in flood-prone and heat-vulnerable districts.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec31\" class=\"Section2\"\u003e \u003ch2\u003e5.2 Directions for Future Research\u003c/h2\u003e \u003cp\u003eFuture research should focus on developing predictive models that integrate real-time meteorological data, environmental surveillance (sewage sampling), and population mobility patterns to identify high-risk transmission zones weeks in advance. Studies examining the thermal stability of oral polio vaccine (OPV) under extreme field temperatures (above 45\u0026deg;C) and community-based interventions to maintain vaccination trust during climate-related disasters would also be valuable.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec32\" class=\"Section2\"\u003e \u003ch2\u003e5.3 Policy-Level Recommendations\u003c/h2\u003e \u003cp\u003eAt the policy level, integration of climate adaptation strategies into the Global Polio Eradication Initiative (GPEI) framework is essential. This includes strengthening water, sanitation, and hygiene (WASH) infrastructure in climate-vulnerable areas and training polio teams in rapid response to extreme weather events. Without such adaptations, climate change will continue to act as a force multiplier, threatening the final stages of global polio eradication.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec33\" class=\"Section2\"\u003e \u003ch2\u003e5.4 Call for Multidisciplinary Collaboration\u003c/h2\u003e \u003cp\u003eAddressing these gaps through multidisciplinary collaboration between epidemiologists, climatologists, and public health planners can help build more robust, resilient systems capable of sustaining progress toward a polio-free world.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eClimate change serves as a significant force multiplier for Wild Poliovirus Type 1 (WPV1) transmission in Sindh province. Between 2015 and 2025, extreme heatwaves, recurrent flooding, and altered monsoon patterns repeatedly disrupted polio eradication activities by damaging health infrastructure, compromising cold-chain systems, and impairing water and sanitation services. These climatic events also triggered large-scale population displacement, which facilitated further poliovirus spread. Consequently, climate-related disruptions have compounded longstanding challenges such as vaccine hesitancy and operational limitations. To achieve sustained progress, polio eradication strategies must evolve from conventional static models to climate-resilient public health systems. National Emergency Action Plans and the Global Polio Eradication Initiative should integrate climatological forecasting, dynamic micro-planning, and strengthened water, sanitation, and hygiene (WASH) infrastructure. Without such adaptive measures, climate change will continue to undermine decades of progress and threaten the global goal of polio eradication.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eClinical trial number:\u0026nbsp;\u003c/strong\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDr. Sharaf Uddin Behan conceptualized the study, developed the research framework, and contributed to the literature search strategy. Dr. Mishal conducted the literature search and performed data screening and extraction. Ms. Huma Nisar assisted in literature screening, data organization, and contributed to drafting the results section. Dr. Nabeela Hamza reviewed and synthesized the climate-related literature and contributed to writing the introduction and climate change sections. Dr. Hira Chachar contributed to the synthesis of epidemiological data, and drafting of the results section. Dr. Sonia assisted in data extraction, analysis of polio surveillance reports, and drafting the Discussion section. Mr. Khan Muhammad contributed to the methodology section and ensured PRISMA compliance. Ms. Rubab Soomro reviewed the literature on population displacement and vaccine campaign disruptions and assisted in writing the limitations section. Ms. Sadia Ahmed contributed to drafting the future Implications and recommendations section and helped with overall manuscript formatting. Dr. Aamir Hussain provided domain expertise on polio eradication in Sindh, constructed figure, performed reference management, and finalized the submission. He also served as the corresponding author. However, all the authors agree to be equally accountable for all aspects of the work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical trial number:\u0026nbsp;\u003c/strong\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funding was involved in conducting the current study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo datasets were generated or analysed during the current study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eGlobal Polio Eradication Initiative. 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Islamabad: NEOC; 2024. \u003c/li\u003e\n\u003cli\u003eZaidi S. Community perceptions of vaccination during disaster recovery. Disasters. 2024;48(1):88-102.\u003c/li\u003e\n\u003cli\u003eMemon Z. Cold chain integrity in extreme heat: A cross-sectional study in Larkana. Pak J Med Sci. 2021;37(3):650-655. \u003c/li\u003e\n\u003cli\u003eBandyopadhyay AS. One Health approach to polio eradication. Nat Med. 2024;30:12-14. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-public-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Public Health](https://link.springer.com/journal/12982)","snPcode":"12982","submissionUrl":"https://submission.springernature.com/new-submission/12982/3","title":"Discover Public Health","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Climate change, Poliovirus, Polio Eradication, Immunization, Sindh, Heatwaves, Floods, Environmental Surveillance, Vaccination Campaigns, Population Displacement","lastPublishedDoi":"10.21203/rs.3.rs-9254205/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9254205/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn Sindh, Karachi and Hyderabad, have remained persistent reservoirs for Wild Poliovirus Type 1 (WPV1). Climate change acts as a significant force multiplier for WPV1 transmission. Traditional eradication strategies mainly focus on vaccine hesitancy and operational gaps. However, the role of climate change remains underexplored. This review examines the impact of climatic variables on polio eradication efforts in Sindh from 2015 to 2025. A narrative review with PRISMA guidelines, have covered heatwaves, flooding, precipitation changes, vaccination disruptions, and poliovirus risks. Data came from PubMed, The Lancet, WHO surveillance reports, and Pakistan Meteorological Department datasets. The 2022 Pakistan floods damaged 888 health facilities, disrupting polio vaccination campaigns and contributing to a surge in polio cases from 1 in 2021 to 20 in 2022. Extreme weather events showed a strong temporal association with transmission spikes, with SIAs reduced by 34% in Northern Sindh post-floods. Climate-induced disruptions, including compromised cold-chain logistics and water/sanitation infrastructure damage, exacerbated poliovirus transmission and hindered eradication efforts. Eradication strategies must shift from static models to climate-resilient systems. Failure to integrate climatological data into public health planning threatens the global eradication goal.\u003c/p\u003e","manuscriptTitle":"Is Climate Change Undermining Polio Eradication Efforts in Sindh, Pakistan? A Comprehensive Evidence from 2015–2025","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-07 16:50:15","doi":"10.21203/rs.3.rs-9254205/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-06T16:29:28+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-31T09:00:16+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-31T08:59:34+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Public Health","date":"2026-03-28T16:23:20+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-public-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Public Health](https://link.springer.com/journal/12982)","snPcode":"12982","submissionUrl":"https://submission.springernature.com/new-submission/12982/3","title":"Discover Public Health","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"0badd7c3-eae2-4ff1-8fe4-48f5e83152c9","owner":[],"postedDate":"April 7th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-30T08:23:35+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-07 16:50:15","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9254205","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9254205","identity":"rs-9254205","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}