Outcomes mapping study for childhood vaccination communication: too few concepts were measured in too many ways.

Objectives: The objectives of this article are to (1) comprehensively catalog outcomes measured in trials of childhood vaccination communication interventions and (2) analyze patterns and trends in outcome selection. To achieve these objectives, we developed a Trial Outcomes Map for vaccination communication.

Study Design: We searched the Cochrane Central Register of Controlled Trials for trials of childhood vaccination communication interventions, extracting verbatim all outcome information from included trials. Through thematic grouping, we categorized outcomes based on conceptual similarities, forming a Trial Outcomes Map.

Results: We identified 112 relevant trials containing 209 outcomes. Thematic analysis revealed three overarching Outcome Categories: consumer-, vaccination-, and health system-related outcomes. These categories contain 21 Outcome Types (eg, "knowledge," "cost"), measured using 66 different Outcome Variables. Vaccination outcomes were measured most frequently and health system-related outcomes least frequently. Consumer outcomes are increasingly measured in more recent trials.

Conclusion: The number of measures used for the same outcomes complicates data synthesis and interpretation. Despite recent trends toward including consumer outcomes, intermediate outcome measurement is lacking, hampering understanding of how and why vaccination communication interventions do or do not work. This Map may improve outcome consistency in future trials and will contribute to a forthcoming core outcome set.