Key factors in complex public health interventions to address vaccine hesitancy using a multidisciplinary approach: the VAX-TRUST project.

The VAX-TRUST project addresses vaccine hesitancy in seven European countries with a systematic and evidence-based approach. Interventions, targeting healthcare professionals, draw from behavioural and social theories. A checklist, inspired by the TIDieR (Template for Intervention Description and Replication), ensures a detailed description of actions, transparency and replicability. The intervention development process begins with collaborative meetings and systematic revisions, concluding with external evaluations for replicability in diverse public health contexts. This study aims to provide valuable insights for future complex interventions in public health, based on lessons learnt to reduce the risk of vaccine-preventable diseases. The analysis of educational interventions within the VAX-TRUST project has led to the definition of precise guidelines to ensure their replicability and adaptation to various contexts, attempting to establish a universally applicable approach. Active participant engagement and consideration of local social dynamics, beyond information transmission, have emerged as key factors to improve intervention effectiveness. Various educational tools and collaboration with academic institutions have contributed to strengthening credibility.