The influence of partisanship on the roots of anti-vaccine attitudes in the context of the COVID-19 pandemic

This study identifies the underlying drivers of vaccine hesitancy by analyzing political factors, perceptions of vaccine safety, socioeconomic characteristics, and communication variables. We created a partisanship score using supervised machine learning algorithms with the random forest method to assess the influence of political orientations on the roots of COVID-19 vaccine rejection attitudes. This score was then tested empirically using sociodemographic data from a public opinion survey conducted with a sample of the Brazilian population. Based on the weight of evidence (WoE), the attribute relevance analysis revealed key characteristics of citizens who rejected the COVID-19 vaccine in Brazil, highlighting perceptions of vaccine safety and political variables. The data showed that citizens more loyal to then-president Jair Bolsonaro, a vocal vaccine skeptic, were less likely to get vaccinated. They also demonstrated higher perceptions of vaccine-related risks and were more prone to believing in conspiracy theories and misinformation surrounding the vaccine. The methodology developed in this study can be applied to other populations globally to better understand the roots of anti-vaccine attitudes, particularly the influence of political factors. • Main variables related to COVID-19 vaccine rejection were identified: distrust of the safety of the vaccine; support for anti-vaccine president and belief in fake news about the COVID-19 vaccine. • The roots of this distrust were predominantly political and ideological. • Conservative ideology not only lowered the perceived risk of the virus but also increased the perceived risk of the vaccine and belief in fake news. • The research highlights the powerful influence of contextual factors, particularly political bias, which proved to be a more significant predictor of vaccine hesitancy than socioeconomic variables such as income, age, education, religion, or region.