Vaccination Attitudes Examination (VAX) Scale: a Bifactor-ESEM approach in a youth sample (15-24 years).

BACKGROUND: The Vaccination Attitudes Examination (VAX) Scale is a widely used scale designed to measure general attitudes toward vaccinations. However, evidence for the VAX's structural, convergent, and discriminant validity is still limited, especially in youth samples. METHODS: The present study examined the psychometric multidimensionality and evidence of convergent and discriminant validity of the VAX using the bifactor-exploratory structural equation modeling approach (bifactor-ESEM). Using a sample of 803 Serbian adolescents and young adults (Mage = 18.23, SDage = 2.66, age range = 15-24 years, 59.2% female), we contrasted the original four-factor model of the VAX with alternative solutions (ESEM, bifactor-CFA, and bifactor-ESEM), and investigated associations between vaccination attitudes and a variety of external criteria. RESULTS: The results supported the bifactor-ESEM solution with one general factor of vaccination attitudes and four specific factors (Mistrust of vaccine benefit, Worries about unforeseen future effects, Concerns about commercial profiteering, and Preference for natural immunity) as the best representation of the data. The general factor was well-defined, and three specific factors showed good validity and specificity after the general factor was taken into account. The results of convergent validity analyses showed that the general factor of vaccine attitudes and one specific factor (Mistrust of vaccine benefit) were good predictors of vaccine conspiracy beliefs, attitudes towards COVID-19 vaccination, intention to get vaccinated against COVID-19, and trust in healthcare. The remaining three specific factors' contributions to external criteria were generally weak and nonsignificant. Evidence of the discriminant validity of the VAX scores was supported by weak positive associations of the general factor with medical fears and paranoid worry. CONCLUSIONS: The present findings indicate that distinguishing general and specific components of vaccination attitudes offers a more nuanced assessment and understanding of vaccination attitudes.