Paranoia affected COVID-19 vaccine refusal by increasing beliefs in conspiracy theories and mistrust of science

Introduction: Psychological determinants of COVID-19 vaccination have been widely studied since the onset of the pandemic, yet little is known about how these factors evolved once vaccines became available. This study addresses this gap by examining psychological predictors of vaccination attitudes and behavior during Italy's third wave (spring 2021), a phase marked by widespread vaccine access and persistent public uncertainty. Methods: A total of 375 adults completed standardized measures of anxiety, depression, death anxiety, paranoia, mistrust in science, mistrust in scientific communication, and conspiracy beliefs. Vaccine intentions were assessed through perceived usefulness and safety, and by actual uptake. Using structural equation modeling with Huber-White robust estimation and bias-corrected bootstrapping, we tested a mediation model linking psychological factors to vaccine evaluation and behavior. Results: The analysis revealed that paranoia exerted a significant indirect effect on both vaccine evaluation and uptake, mediated by mistrust in science and conspiracy beliefs. Death anxiety displayed a small but direct positive association with vaccination behavior. Discussion: These findings suggest that while contextual factors such as vaccine availability shape overall attitudes, paranoia and related distrust remain stable psychological barriers to vaccine acceptance. The present study extends prior research by clarifying how enduring cognitive biases interact with situational context to influence vaccination decisions, with implications for public health communication strategies.