Institutional drivers of newborn hepatitis B vaccine disparities: A multi-hospital analysis in Washington, DC, 2017-2023.

Despite universal newborn hepatitis B vaccination recommendations, birth dose coverage remains suboptimal with persistent racial disparities. While individual-level factors are well-studied, institutional practices' role in vaccination outcomes remains poorly understood. We conducted a retrospective cohort study of 87,246 singleton births across eight Washington, DC hospitals from 2017-2023, using multilevel mixed-effects logistic regression to examine institutional disparities in vaccine refusal. Overall refusal rate was 6.7%, declining from 12.1% in 2017 to 3.5% in 2023. Hospital-specific rates varied dramatically, from near-zero to over 50%. Multilevel analysis revealed 31.1% of refusal variance was attributable to between-hospital and between-year differences, with stable hospital characteristics accounting for 71% of this contextual variance (22.1% of total) and temporal trends accounting for 29% (9.0% of total). Analysis of hospital-specific temporal trajectories revealed marked heterogeneity in response speed to the 2018 ACIP policy change: safety-net hospitals achieved target refusal rates within one year, while institutions with higher baseline refusal required 2-4 y. In contrast to national adult vaccination patterns where White individuals have higher coverage, White infants had lower refusal odds than Black infants after covariate adjustment, suggesting institutional practices may be associated with context-specific disparities that differ from broader population patterns. Sensitivity analyses confirmed robustness of findings. Substantial institutional variation in vaccination practices is associated with disparities beyond what would be expected from patient demographics alone, highlighting the need for system-level interventions targeting organizational factors to achieve equitable vaccination coverage.