Determinants of COVID-19 vaccine hesitancy: questionnaire development and validation

Vaccine hesitancy presents one of the critical constraints in combating COVID-19 pandemic. The aim of this study was to develop and validate an instrument for measuring factors that contribute to COVID-19 vaccine hesitancy.The key constructs in the study instrument were factors that constitute the "3C" model of vaccine hesitancy: Confidence, Complacency and Convenience. Using a cross-sectional, online survey design, the 8-item COVID-19 Vaccine Hesitancy Questionnaire was administered to a sample of 667 adult citizens of Serbia in December 2020. We used confirmatory factor analysis to investigate the model that assumes three latent variables. To ensure that the instrument measures the same constructs in different groups, the measurement invariance examination was conducted. To examine criterion validity, Spearman's correlation was applied to determine the association between the instrument total score and the single-item measuring the likelihood of getting vaccinated against SARS-CoV-2.Confirmatory factor analysis established the three-factor structure, with subscales fitting within the "3C" model of vaccine hesitancy comprising confidence, convenience and complacency. The full scalar invariance was found across gender, and the partial scalar invariance was achieved for the age, region and education level. A higher level of the COVID-19 vaccine hesitancy was associated with the lower likelihood to get vaccinated against the SARS-CoV-2 virus.Our scale is brief and consistent, maintaining a good fit across key socio-demographic subgroups. This result implies that the scale could be useful for quick assessment of COVID-19 vaccine hesitancy in various target populations.