The role of institutional trust in shaping the relationship between vaccine concerns and ongoing COVID-19 vaccination in a US national cohort

Concerns about vaccine safety and efficacy and institutional trust are well-established determinants of vaccine uptake, yet little is known about the extent to which institutional trust buffers or amplifies the behavioral effects of vaccine-related uncertainty. Using data from 4,253 adults in the CHASING COVID Cohort who completed their primary vaccine series, we examined whether trust in public health institutions or healthcare providers modified the association between vaccine concerns and receipt of an additional COVID-19 vaccine dose. Adjusted log-binomial regression models estimated risk ratios (aRRs) and 95% CIs, with effect modification assessed on multiplicative and additive scales. The association between not endorsing vaccine concerns and continued vaccination was stronger among those without trust in public health institutions (aRR = 2.38 [95% CI, 1.90-2.97]) than among those with trust (aRR = 1.34 [95% CI, 1.22-1.46]), while antagonism on the additive scale (RERI = $-$0.68; P <.01) indicated overlapping pathways as having no vaccine concerns added little to the likelihood of continued vaccination among those with trust in public health institutions. Provider trust showed modest additive effects (RERI = 0.16; P = .08), suggesting greater-than-additive influences. Together, findings highlight institutional trust as an important contextual determinant shaping how vaccine-related beliefs are enacted and underscoring its importance for promoting ongoing vaccination uptake.