Are individuals with persistently high conspiracy mentality also persistently vaccine-hesitant? Findings from a three-wave panel study

Conspiracy mentality and vaccine hesitancy are frequently linked, yet most evidence is cross-sectional and cannot separate stable between-person differences from within-person change. Thus, it remains unclear whether conspiracy mentality drives vaccine hesitancy or vice versa. In addition, trust in science has been proposed as a key pathway connecting the two. To tackle these questions, we carried out a three-wave panel of adults (N = 574, Mean age = 52.80, SD = 15.88; 47.4 % men), who were followed over four months. Conspiracy mentality, trust in science, and vaccine hesitancy were measured at each wave. Longitudinal measurement invariance was evaluated prior to modeling. In the cross-lagged panel model, a small cross-lag emerged from conspiracy mentality at Wave 2 to vaccine hesitancy at Wave 3; other cross-lags were non-significant. In the random-intercept cross-lagged panel model, all within-person cross-lags were non-significant, while the random-intercept correlation between the two constructs was strong, indicating substantial trait-level overlap. A three-wave, time-lagged mediation model showed a significant indirect effect from conspiracy mentality to vaccine hesitancy via lower trust in science. The findings suggest that conspiracy mentality and vaccine hesitancy co-exist as stable, correlated dispositions rather than displaying robust short-term within-person effects. At the population level, lower trust in science appears to be a key pathway linking conspiracy mentality to higher vaccine hesitancy. Interventions should therefore emphasize building trust in science.