The research question revolves around understanding the complex interplay between mass polio vaccination campaigns and health systems in Ethiopia, India, and Nigeria, specifically focusing on the impacts on frontline health worker (FLHW) motivation and vaccine hesitancy. The study's context is the long-standing debate regarding the effects of vertical health programs (like mass vaccination) on broader health systems. Previous research often analyzed these impacts in isolation from the program's goals and categorized them simply as positive or negative, neglecting the dynamic and interconnected nature of health systems. This study aims to move beyond this simplistic approach by employing a complex adaptive systems (CAS) lens, acknowledging the path dependency and unintended consequences within these systems. The importance of the study lies in its potential to provide valuable insights for designing more effective and sustainable vaccination campaigns, particularly in the context of the ongoing global health challenges such as the COVID-19 pandemic. The study uses a CAS framework to analyze how the interactions between polio campaigns and health systems influence FLHW motivation and vaccine hesitancy, ultimately affecting campaign coverage. The researchers utilize a CAS lens to address the limitations of previous research methodologies, which often failed to adequately capture the complexity and dynamic interactions within health systems. By explicitly modeling these interactions, the study aims to offer a more nuanced and comprehensive understanding of the long-term effects of mass vaccination campaigns.

The paper begins by referencing the 1995 Taylor Commission report, which assessed the impact of polio campaigns in the Americas. While acknowledging varied effects, the report cautioned against extrapolation to other regions and established two key approaches: evaluating the effects separately from the program's success and categorizing impacts as simply positive or negative. Subsequent research, though sophisticated, largely maintained these methods, despite limitations. Several studies highlighted the tension between campaign-based and routine delivery strategies, and the difficulties in leveraging eradication initiatives for broader health system strengthening. However, these analyses generally remained within the framework of separating impacts by health system components and using a binary positive/negative categorization. Recognizing the limitations of these approaches, several researchers in 2014 emphasized the need for better frameworks to account for the complex and dynamic nature of health systems. The study highlights the underutilization of systems thinking approaches in global health, despite their increasing use in other complex phenomena. The advent of global COVID-19 vaccination campaigns has renewed interest in maximizing campaign effectiveness and designing campaigns to benefit the health system. The authors argue that moving beyond these prevailing ways of thinking requires viewing health systems as complex, dynamic, and tightly linked entities, explicitly addressing the relationships between system elements that influence outcomes over time. The paper positions its use of a CAS lens as crucial to addressing this gap in the existing literature.

This study employs a qualitative approach using data from two previous studies: the Polio Eradication Impacts Study (2011-2012) and the Synthesis and Translation of Research and Innovations from Polio Eradication (STRIPE) study (2019). The Polio Eradication Impacts Study used a multimethods approach to explore the relationship between the Global Polio Eradication Initiative (GPEI), routine immunization (RI), and primary health care (PHC) in seven study sites. The STRIPE study mapped explicit and tacit knowledge from polio eradication at the global and national levels. Both studies included frontline, district, and national-level respondents; STRIPE also included global actors. Data consisted of semistructured interviews. The analysis focused on three countries: Ethiopia, India, and Nigeria, selected for their substantial polio campaign activity and diverse contexts. The researchers constructed a causal loop diagram (CLD) from the interview data, incorporating findings from literature reviews on polio eradication in these countries. The CLD building process involved several steps. First, a list of variables mediating the relationship between campaigns and health systems was compiled from previous studies, categorized into five themes: FLHWs; supervisory structures; politics and government-community relations; health system quality and responsiveness; and reliance on mass campaigns. Coded material from both studies was collated according to these themes. Three analysts independently reviewed the data, focusing on one study country each, generating memos on each theme. Weekly review sessions facilitated cross-country comparisons and led to the development of three country-specific CLDs. These country-specific CLDs were then combined to form an overall CLD representing consistent dynamics across all study countries. The team iterated extensively to ensure accuracy and interpretability, with validation from co-authors in each country. This approach employed a strictly qualitative analysis adhering to high-quality, inductive theory development standards. The CLD visually represents interactions between polio campaigns and health systems, illustrating feedback loops and highlighting path dependency.

The CLD revealed several key interactions. At the policy level, the single-disease focus of the GPEI led to the creation of parallel systems and reduced accountability to community priorities. Parallelism, driven by a short-term focus on eradication, led to increased campaign frequency in weaker health systems. This intensified demands on already strained resources and personnel. At the FLHW level, parallel systems resulted in cascading effects that demotivated workers, primarily due to increased fatigue from excessive campaign frequency and uncoordinated workflows with multiple supervisors and reporting requirements. FLHWs also had existing responsibilities for a wide range of health initiatives that were not supported or coordinated with polio campaigns. The lack of rational workloads led to significant fatigue and negatively impacted motivation. This fatigue was a slow-burning issue, becoming particularly intense over years of repeated campaigns. Co-delivery, however, emerged as a strategy that mitigated some negative effects, improving workflows and reducing fatigue. Community-level findings revealed a strong link between vaccine hesitancy and trust in the overall health system, particularly in areas with frequent campaigns and weak health infrastructure. When health systems were unresponsive to community needs, vaccine refusal sometimes became a strategy to pressure the government for attention to other urgent health issues. Communities expressed frustration over the focus on polio while basic healthcare services remained lacking. Co-delivery again emerged as a strategy that counteracted this negative dynamic, increasing community trust as campaigns provided additional services beyond polio vaccination. Importantly, the study found that these interactions developed over years, leading to path-dependent consequences that diminished the long-term effectiveness of polio campaigns in areas with weaker health systems.

The study's findings address the research question by demonstrating how the design of mass vaccination campaigns, specifically the creation of parallel systems and frequent campaigns in weak health systems, significantly impacts health worker motivation and community vaccine uptake. The significance of these findings lies in their implication for the design and implementation of future mass vaccination campaigns. The CLD methodology allowed for a more nuanced understanding of the complex interactions between campaigns and health systems, revealing the importance of considering path dependency and feedback loops. The results highlight the need to move beyond short-term goals of eradication and incorporate a long-term perspective focusing on health system strengthening and responsiveness to community needs. The findings are relevant to the field of global health by providing evidence for a systems-thinking approach to campaign design, emphasizing the interconnectedness of health system components and the potential for unintended consequences of overly frequent or poorly integrated campaigns. The study directly challenges the prevailing practice of analyzing vertical program impact in isolation and suggests a more holistic approach that considers the dynamic interplay between campaigns and health systems.

This study demonstrates that the design of mass vaccination campaigns significantly impacts their long-term effectiveness. Frequent campaigns delivered through parallel systems, without consideration for the dynamic impacts on health systems, lead to decreased health worker motivation and increased vaccine hesitancy, particularly in areas with weaker health systems. Co-delivery of interventions is a key strategy to mitigate these negative effects. Future research should focus on further exploring the dynamics of co-delivery and developing implementation strategies that ensure long-term sustainability of health services, going beyond short-term eradication goals. The study's findings highlight the critical need for a systems-thinking approach that considers path dependency and the interconnectedness of health system components in the design of effective and sustainable vaccination programs.

The study's qualitative nature limits the generalizability of findings to a broader range of contexts. The focus on three specific countries, while providing rich detail, may not fully capture the diversity of experiences across all settings. While the study aimed for diverse respondent representation, incorporating additional perspectives from caregivers and health managers outside the polio program could have further enriched the analysis. Data availability might also be a factor to consider when accessing and utilizing the information for research purposes.