Development and Validation of an Extended Adult Vaccine Hesitancy Scale in Greek-Speaking Populations

Vaccine hesitancy (VH) is a complex global public health threat requiring validated tools for its assessment globally. This study aimed to evaluate an extended adult Vaccine Hesitancy Scale (aVHS) among Greek-speaking adults.

This study evaluated a newly developed extended version of a widely used aVHS, incorporating five additional items on long-term safety, risk-benefit evaluation, vaccine-related harm, scientific credibility, and perceived alternatives, on a cross-sectional sample of 491 adults in Greece and Cyprus. Cross-cultural adaptation of the extended aVHS involved translation, back-translation, and pilot testing. Structural validity was assessed using parallel analysis, exploratory factor analysis (EFA), and reliability using Cronbach's α and McDonald's ω. Criterion validity was assessed against focus-group classification using ROC analysis in 68 participants.

A one-factor EFA solution appeared the most parsimonious, showing strong loadings for the original and extended aVHS (0.67-0.86 and 0.65-0.87), with similar explained variance (60.31% and 60.06%). The one-factor solution was confirmed by parallel analysis for both scales. Internal consistency was excellent, and slightly higher for the extended than the original aVHS (α = 0.95; ω = 0.95 vs. α = 0.92; ω = 0.93). The five newly added items performed strongly, with item-rest correlations of 0.69-0.85 and loadings of 0.72-0.87. Criterion validity was excellent, with a slightly higher AUC (0.991 vs. 0.981) and numerically higher classification performance for the extended than the original aVHS.

The extended aVHS is a psychometrically coherent tool that improves the performance of the original scale among Greek-speaking individuals. This scale may enhance VH surveillance, aiding targeted vaccination communication strategies.