Date of Award

2026

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Psychology

Specialization

Clinical Psychology

Department

Psychology

First Advisor

Mark L. Robbins

Abstract

Purpose. To assess the measurement invariance of four novel Transtheoretical Model (TTM)-based measures for readiness to get vaccinated for COVID-19. Design. Cross-sectional.

Setting. Online survey study in the United States (US).

Participants. 1169 US-based adults aged 18-85.

Measures. Demographics, Stage of Change, Vaccination History, Decisional Balance, Self-efficacy, Myths, and Barriers to COVID-19 vaccination.

Analyses. Multigroup confirmatory factor analyses with increased restraints on model parameters to assess configural (no constraints), metric (factor loadings constrained), and scalar invariance (factor loadings and item intercepts constrained) in a sequential manner.

Results. Decisional Balance, Myths, and Barriers demonstrated scalar invariance across during- and post-pandemic contexts, with Decisional Balance and Myths also exhibiting strict invariance. In contrast, Self-efficacy did not demonstrate configural invariance across contexts. An updated version of the Self-efficacy scales showed acceptable model fit using the post-pandemic sample.

Conclusion. Decisional Balance, Myths, and Barriers may be used in both current interventions and future research aimed at increasing vaccine uptake, regardless of social context. In contrast, the original Self-efficacy measure should not be used across contexts. However, the updated Self-efficacy scale, developed using the post-pandemic sample, may serve as a reliable, context-specific tool for research and practice.

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