Shared and vaccine-specific factors associated with COVID-19 and influenza vaccination intentions among adults in Poland: a COM-B-informed cross-sectional study.

Introduction: Vaccination intentions reflect both vaccine-specific attitudes and cognitive, social, and practical conditions. This study aimed to identify shared and vaccine-specific factors associated with COVID-19 and influenza vaccination intentions among adults in Poland using a Capability, Opportunity, Motivation-Behavior (COM-B) model-informed comparative approach and to assess the incremental contribution of vaccine hesitancy. Methods: A cross-sectional computer-assisted web survey was conducted in May 2026 among 3,000 adults recruited from a national online panel using quota controls for age, sex, education, place of residence, and macroregion. Measures included a COM-B-informed item set, the Polish Adult Vaccine Hesitancy Scale, the short version of European Health Literacy Survey Questionnaire, the Conspiracy Mentality Questionnaire, and sociodemographic, health-related, political, religious, and social media variables. The item set was evaluated through exploratory and confirmatory factor analyses in independent subsamples, followed by theory-ordered hierarchical logistic regression, Results: Intention was reported by 18.2% of respondents for COVID-19 vaccination and 31.5% for influenza vaccination. Psychometric analyses supported retention of three theory-defined COM-B domain indicators, although Capability and Opportunity showed limited empirical separation. Capability was positively associated with COVID-19 and influenza vaccination intentions (OR = 1.31 and 1.74, respectively), as was Motivation (OR = 2.64 and 1.56). Opportunity showed inverse adjusted associations (OR = 0.72 and 0.73). Vaccine hesitancy added explanatory value in both models and showed a nonlinear association with influenza intention. Political preference showed a vaccine-specific pattern: compared with supporters of Law and Justice, supporters of the far-right Confederation party had lower odds of COVID-19 vaccination intention (OR = 0.50), whereas no corresponding association was observed for influenza vaccination intention. Non-participation in the 2023 parliamentary election was associated with lower odds of both intentions. Nagelkerke Conclusion: The shared pattern across outcomes supports COM-B as an organizing framework, while the incremental contribution of hesitancy and differences in political and health-related correlates demonstrate the vaccine-specific context of vaccination intentions. COVID-19 intention remained more politically differentiated. Vaccination-promotion strategies should combine behavioral diagnosis with attention to the political context of each vaccine.