The 8C model of vaccination readiness: A common framework to facilitate cross-study comparisons.

Several factors can potentially influence an individuals vaccination readiness. To facilitate cross-study comparisons, it is essential that researchers use a shared framework to measure these factors. This would not only help determine their relative importance cross different contexts but also would aid in tailoring interventions to enhance vaccine uptake. Historically, five psychological antecedents of vaccination were identified: confidence, complacency, constraints, calculation, and collective responsibility. This 5C scale was later expanded to a 7C model by incorporating two additional components: compliance and conspiracy. Building upon this framework, we propose an eighth component, certification, defined as the persons self-report that, in the past, they have had to provide evidence of vaccination. This component addresses a significant gap in the 7C model, as some individuals reported taking the COVID-19 vaccine primarily to obtain proof of vaccination, a motivation not captured by the 7C model. Our confirmatory factor analysis (N = 406) of a bifactor model of US citizens self-reported COVID-19 vaccination status showed that this eighth component had good psychometric properties and the 8C model had slightly higher criterion validity than the 7C model. We present the 8C model as a framework that provides a richer and more complete descriptions of the factors that determine vaccination readiness and encourage future studies of vaccination readiness to utilise it.