The COVID-19 pandemic, as a shock scenario, provided an opportunity to study the performance of the same policy instrument implemented simultaneously across diverse national contexts. This research addresses the question: How do institutions and political management of COVID-19 vaccination explain the variable performance across Central American countries throughout 2021? The study aimed to first characterize and then account for this performance variation. To operationalize vaccination performance, the study considered aspects addressed in existing literature, integrating three fundamental dimensions: coverage, sufficiency, and sustainability. Each dimension was operationalized through specific indicators linked to different immunization stages (first, second, and third doses), combining public policy metrics—such as population coverage—with epidemiological indicators—such as vaccination speed. This comprehensive analytical framework captures the complexity of the immunization process during a health crisis, particularly relevant for a region that faced the pandemic under adverse structural conditions. The regional analysis is complemented by process tracing within a paired comparison framework, establishing three country pairs: Costa Rica-Panama, El Salvador-Nicaragua, and Honduras-Guatemala. This allowed for a deeper understanding of COVID-19 vaccination performance by examining convergences and divergences between comparable national cases. Empirical research revealed heterogeneous vaccination policy performance across Central America, manifesting in three distinct levels: high (Costa Rica and Panama), intermediate (El Salvador and Nicaragua), and low (Honduras and Guatemala). Rather than simply reproducing expected performance levels based on pre-pandemic factors, this pattern reflected political and institutional factors that this study sought to unravel. The theoretical framework developed in this research generates new analytical perspectives for the field of social policy studies. It builds upon established theories for social policy development in “normal times.” These theories recognize the weight of sectoral factors such as policy legacies, state capacity, and public policy architectures, as well as macro-political factors like political regimes and leadership. This study combined these elements to explain the response to a shock. The work is structured in four main sections: a problematization chapter establishing justification, background, and research object; a theoretical-conceptual framework chapter presenting the methodological design; a comparative regional analysis examining identified dynamics and patterns; and three chapters dedicated to detailed analysis of results obtained through country-pair comparisons.