Social license for vaccination: a mixed-methods analysis of public endorsement determinants

This study examined the multilevel factors associated with vaccine social license in China. It used a social-ecological framework to assess how individual traits, social influences, and institutional trust jointly relate to public recognition of and support for vaccine policies. A cross-sectional online survey was conducted through the Survey Plus platform. A total of 1518 valid responses were included. Measures covered the Big Five personality traits, an eight-item vaccine social license scale (Cronbach’s α = 0.80), trust in information channels, proximal social norms, perceived usefulness, and perceived ease of use. Necessary condition analysis showed that no single condition reached the prespecified necessity threshold of d ≥ 0.10. Government trust had the largest necessity effect, followed by perceived usefulness, government transparency, conscientiousness, and perceived ease of use. In the fuzzy-set qualitative comparative analysis necessity test, proximal social norms reached the consistency threshold of 0.90. fsQCA further identified six sufficient configurational pathways. Two were cross-level integration pathways, and four were multilevel nested pathways. A complementary Light Gradient Boosting Machine with SHapley Additive exPlanations (SHAP) analysis showed that perceived usefulness had the highest predictive importance, followed by proximal social norms. The configurations also showed alternative combinations among institutional trust dimensions. These findings suggest that vaccine social license is associated with multiple combinations of individual, social, and institutional conditions. The results may inform differentiated communication and policy strategies for strengthening public support for vaccination programmes.