Why do Catholics have lower COVID-19 vaccine intentions than atheists? The mediating role of belief in science and moral foundations

The global COVID-19 pandemic underscored the critical need for high vaccination rates to achieve herd immunity. However, vaccine hesitancy remains a significant obstacle. In Poland, a predominantly Catholic country, a substantial portion of the population remains unvaccinated. Existing research links greater religiosity with lower vaccination rates, particularly among Christians. This study addresses the lack of understanding regarding the mechanisms driving this relationship, focusing on the comparison of Polish Catholics and atheists. Three studies explore the mediating roles of belief in science and moral foundations in explaining the observed difference in COVID-19 vaccination intentions between these groups. The importance of this research stems from its implications for the health of believers and the effectiveness of public health initiatives.

Prior research consistently demonstrates a correlation between religiosity and vaccine hesitancy. Studies have shown that highly religious individuals, particularly Christians, exhibit greater reluctance towards COVID-19 vaccination. Cross-national analyses confirm a negative association between Christianity and vaccination rates, while other religions and atheism show no such correlation. However, religiosity is a multifaceted construct. Intrinsic religiosity, characterized by sincere belief and adherence to religious doctrines, has yielded mixed results regarding vaccination intention—some studies showing a negative correlation, others a positive correlation. Extrinsic religiosity, using religion for instrumental purposes, is less studied in this context. Existing explanations for the negative relationship between religiosity and vaccination include mistrust in vaccines, acceptance of conspiracy theories, external health locus of control, and a tendency to believe in information contradicting scientific data. Some posit that religious individuals may feel threatened by science perceived as secular and aiming to disprove their faith. Belief in science, a contrasting worldview to religious belief for some, is also implicated. Religious individuals often demonstrate greater skepticism towards scientific findings. Previous studies have explored the mediating roles of trust in the scientific community and scientific credibility in the relationship between religiosity and vaccination, but these studies typically measure religiosity continuously and lack sufficient atheist representation. This study directly compares believers and atheists while investigating belief in science and moral foundations as mediating factors.

The study comprises three independent studies conducted in Poland between August and November 2023, targeting Catholics and atheists. **Study 1 (n=689):** This study compared COVID-19 vaccination intentions of Catholics and atheists, examining the mediating role of belief in science and the moderating role of group identification. Data were collected via online surveys through a national research panel, with a quota sample reflecting the Polish population's demographic characteristics. Measures included a single-item COVID-19 vaccination intention scale, a group identification scale, and a belief in science scale. A moderated mediation analysis was conducted using PROCESS (Model 8) with bootstrapping. **Study 2 (n=752):** This study focused solely on Catholics (n=752), investigating the mediating role of belief in science in the relationship between intrinsic and extrinsic religious orientation and COVID-19 vaccination intention. The methodology mirrors Study 1, using the same measures and employing PROCESS (Model 4) for mediation analysis. **Study 3 (n=469):** This study explored the mediating role of moral foundations (care, fairness, loyalty, authority, purity) in the relationship between Catholic affiliation and vaccination intention. Using the Polish version of the Moral Foundations Questionnaire, it employed the same survey methodology as Study 1, again utilizing PROCESS (Model 4) for mediation analysis. All studies controlled for demographic variables (age, sex, education). Confirmatory factor analysis (CFA) was performed to validate latent variables before running PROCESS.

**Study 1:** Catholics showed significantly lower COVID-19 vaccination intention than atheists. This relationship was fully mediated by lower belief in science among Catholics. The negative relationship between Catholic affiliation and belief in science was moderated by group identification: stronger identification intensified this negative correlation. Surprisingly, stronger group identification (for both Catholics and atheists) was associated with higher vaccination intention. **Study 2:** Intrinsic religious orientation negatively correlated with vaccination intention, fully mediated by belief in science. Extrinsic religious orientation showed a positive correlation with vaccination intention. **Study 3:** Catholics had lower vaccination intention than atheists, mediated by higher levels of purity and loyalty moral foundations among Catholics. Higher care moral foundations correlated positively with vaccination intention. Authority and fairness moral foundations did not show significant mediating effects.

The findings provide a nuanced understanding of the complex factors influencing COVID-19 vaccination intentions among Polish Catholics and atheists. The mediating role of belief in science highlights the importance of addressing this cognitive factor in interventions aimed at improving vaccine uptake among religious groups. The influence of moral foundations underscores the potential of using targeted communication strategies that appeal to purity and loyalty to increase vaccine acceptance. The study's results suggest that increased belief in science and framing vaccination as an act of loyalty within the religious community might be effective strategies to increase vaccination rates. The study's findings, particularly on the negative relationship between intrinsic religious orientation and belief in science, extend beyond prior research predominantly focused on the US context.

This research provides valuable insights into the determinants of COVID-19 vaccine hesitancy among Polish Catholics and atheists. The study demonstrates the importance of considering belief in science, religious orientation, moral foundations, and group identification in designing effective interventions to increase vaccine uptake. Future research should explore these factors in other cultural and religious contexts and examine the effectiveness of tailored interventions designed to address the identified mediating mechanisms. Longitudinal studies could further clarify the causal relationships between these variables and vaccination behavior.

The study's main limitation is its focus on Polish Catholics and atheists, limiting the generalizability of the findings to other populations and religious groups. The cross-sectional design limits the ability to establish definitive causal relationships. The use of multiple mediation models without correcting for multiple comparisons increases the risk of Type I error. Future research should employ longitudinal studies and broader sampling strategies to address these limitations.