Conceptualising undervaccinated populations in high-income settings: why consensus and clarity matter

Routine immunisation coverage across high income countries is challenged by ongoing decline/attrition and persistent disparities.1 Terminology to describe groups with suboptimal vaccination rates has evolved from “hard-to-reach,” “marginalised,” and “disadvantaged” to “underserved.” Despite differing implicit assumptions, these terms are often used interchangeably, obscuring their distinct biases. Clarity in terminology is important for shaping programme delivery and outreach methods in ways that avoid stigmatising communities.