Background: Instruments designed to assess individual differences in predispositions towards vaccination are useful in predicting vaccination-related outcomes. Despite their importance, there is relatively little evidence regarding the conditions under which these instruments are more predictive. The current research was designed to improve the ability of these kinds of instruments to predict vaccination advocacy by considering the certainty associated with the responses to vaccination scales.
Method: Across two studies, participants completed the Beliefs about Medicines Questionnaire BMQ scale (Study 1) or the Vaccination Attitudes Examination (VAX) scale (Study 2). The certainty participants had in their responses to each scale was either measured (Study 1) or manipulated (Study 2). Intentions to advocate in favor of vaccination served as the criterion measure in both studies.
Results: As expected, the scales significantly predicted vaccination advocacy, contributing to enhancing the predictive validity of the instruments used in the studies. Most relevant, certainty moderated the extent to which these scales predicted vaccination advocacy, with greater consistency between the initial scores and the subsequent advocacy willingness obtained for those with higher certainty.
Conclusions: Certainty can be useful to predict when the relationship between vaccination-related cognitions (i.e., beliefs or attitudes) and advocacy willingness is likely to be stronger.
Keywords: beliefs about medicines questionnaire (BMQ); certainty; confidence; individual differences; meta-cognition; vaccination advocacy; vaccination attitudes examination scale (VAX).