Unscientific mindsets and the gap between past vaccine behaviors and future intentions

Objective: Use of Complementary and Alternative Medicines (CAM) is associated with vaccine hesitancy. However, the nature of—and reasons for—this association are obscure as both CAM and vaccine hesitancy are complex, heterogeneous phenomena. This study aims to identify which aspects of CAM predict vaccine hesitancy and to probe the psychological roots of their association.Methods: In a two-stage survey (N1 = 1905, N2 = 1443), participants from Argentina, Germany and the USA reported vaccine/CAM health behaviors, intentions and beliefs. They also responded to scales probing attitudes to science, individual differences in cognitive styles, and anomalous beliefs.Results: An Item-Response Theoretic model of vaccine responses revealed that, outside of either total acceptance or outright refusal of vaccines, hesitancy reflected a gap between past vaccination behaviors and future behavioral intentions. More than CAM use, vaccine hesitancy was predicted by CAM-relevant health beliefs. An oppositional view of natural vs. biomedical care was central in this regard. Unscientific mindsets—both in attitudes to expertise and in anomalous beliefs—underpinned the psychological similarity of CAM beliefs and vaccine hesitancy.Conclusions: The relationship between CAM and vaccine hesitancy is primarily a matter of health-relevant beliefs centered on natural vs. scientific medicine. This relationship—and in particular, a gap between past vaccine behaviors and future behavioral intentions—reflects fundamentally unscientific mindsets. Thus, a key challenge in addressing this form of vaccine hesitancy is one of perspective taking: Scientists must find persuasive reasons to vaccinate which appeal to people who do not see science as the main route to medical knowledge.