Psychometric properties and measurement invariance of the Vaccination Attitudes Examination Scale (VAX) in a Spanish sample

In these times of pandemic, the acceptance or rejection of vaccines has become increasingly clear, with a considerable rise in the anti-vaccine movement in Spain. It is important to understand the attitudes that lead a person to refuse vaccination in order to develop more effective public health campaigns. The objective of this study has been to study the psychometric properties and measurement invariance of the Vaccination Attitudes Examination (VAX) scale in a Spanish sample. Confirmatory factor analysis and structural equation modelling have been used to study the psychometric properties of the VAX. Likewise, the measurement invariance by gender and educational level has been studied. The structure of four related factors for VAX is confirmed, as well as its predictive value, since the factor 'trust in the benefit of the vaccine' clearly predicts the choice to be vaccinated. The strong measurement invariance by gender and educational level is also confirmed. The comparison of latent means between groups indicates that there are no differences by gender in any factor. However, people with a high educational level present higher scores in factors 'concern about unforeseen future effects', 'concern about commercial effects and speculation' and 'preference for natural immunity'. The VAX is presented as a reliable and valid tool to assess four different factors related to attitudes towards vaccines in Spain. Future studies of its cross-cultural invariance may help to determine the main factors that lead people not to be vaccinated in order to develop more effective public health campaigns.