Psychometric Properties of the Social COVID-19 Vaccine Misinformation Scale (Smcov-19VMS-46}

Introduction: Vaccine confidence within individuals or communities at large exist on a spectrum, ranging from full acceptance to outright refusal. The rapid spread of misinformation on social media platforms since the outbreak of the novel coronavirus in 2019 prompted the World Health Organization (WHO) to coin the term "Infodemic," highlighting the role of social media in spreading anti-vaccine discourse globally.

Objective: The objective of this study was to develop and test the psychometric properties of the 46 item Social Media Covid-19 Vaccine Misinformation Scale assessing Social Media Covid-19 Vaccine Misinformation, Social Media User Behavior and Social Media User's Confidence on Covid-19 vaccine related content.

Methods: A total of 455 participants (age >18) were recruited across ten states of U.S with high and low vaccine uptake. The 455 respondents completed a demographic questionnaire, the 20 item Internet Addiction test and the 46 item Social Media Covid-19 Vaccine Misinformation Scale.

Results: The Doornik–Hansen test indicated that the data violated the assumption of multivariate normality, χ²(92) = 4274.03, p < .0001; accordingly, estimation was conducted using the weighted least squares mean and variance adjustment (WLSMV) method in Mplus, with 5,000 bias‑corrected bootstrap samples. The initial confirmatory factor analysis (CFA) of the hypothesized three‑factor model comprising Consumption, Confidence, and Sharing showed poor fit, χ²(984) = 2030.70, p < .0001, RMSEA = 0.068 (90% CI [0.064, 0.073]), CFI = 0.868, TLI = 0.861, SRMR = 0.089. High correlations between Consumption and Sharing (r = .898) and modification indices suggested more parsimonious structure. Guided by these indices, a bifactor model was tested, including a general factor, Social Media COVID‑19 Vaccine Misinformation, and two group factors: Social Media User Behavior (SMUB) and Confidence. The bifactor model demonstrated good fit, χ²(938) = 2146.44, p < .0001, RMSEA = 0.053 (90% CI [0.050, 0.056], CFI = 0.93, TLI = 0.92, SRMR = 0.054, χ²/df = 2.2). Cronbach’s α values for the general factor (α = .94) and group factors SMUB (α = .95) and Confidence (α = .93) indicated excellent internal consistency, with average inter‑item correlations within the desirable range (0.15–0.50), supporting the psychometric soundness of the SMCov‑19VMS‑46 scale.

Conclusion: The 46 item SMCov-19VMS scale can be reliably used to measure the construct of social media Covid-19 vaccine misinformation. The practical applicability of the SMCov-19VMS scale may vary across different cultural and demographic groups, necessitating further validation in diverse populations to maximize the generalizability of the findings.