Under-vaccination as a systems failure: A Monte Carlo simulation of the 2025 CDC/ACIP hepatitis B birth-dose policy...

In 2025, the CDC/ACIP reclassified the hepatitis B (HBV) birth-dose recommendation from universal vaccination to a shared clinical decision-making (SCDM) model. U.S. adult HBV vaccination rates remain stagnant at 30-32%, reflecting systemic delivery failures. The projected impact of this policy shift and whether multi-level interventions can protect vulnerable populations remains unquantified.

We developed a Monte Carlo simulation (N = 50,000 iterations) projecting U.S. vaccination outcomes from 2025 to 2035 across five scenarios: (A) policy-only; (B) hospital standing orders; (C) EHR-driven clinic workflow optimization; (D) community health worker (CHW) outreach; and (E) a comprehensive multi-level intervention. Parameters derived from published surveillance data, clinical trials, and implementation studies. Primary outcomes included birth-dose coverage, adult series completion, perinatal infections, and chronic HBV cases.

Under Policy-Only (Scenario A), birth-dose coverage fell from 91.8% to 75.7% by Year 10, yielding 19,306 perinatal HBV infections (95% CrI: 15,851-24,279) and 17,376 chronic cases. The comprehensive intervention (Scenario E) maintained birth-dose coverage at 89.7% (95% CrI: 80.3-97.0%) and adult vaccination at 95.0% by Year 10, reducing perinatal infections to 1952 (95% CrI: 729-3869)-equivalent to 10.4 million additional adult vaccinations over Policy-Only. Maternal screening sensitivity was the strongest predictor of perinatal outcomes (r = -0.909).

The 2025 SCDM policy, absent structural safeguards, is projected to reduce perinatal HBV protection and widen health disparities over the next decade. A comprehensive multi-level intervention-combining standing orders, EHR-driven workflows, and CHW outreach-is necessary to offset projected harm. Policy revision alone is insufficient; protecting vulnerable populations requires fundamental redesign of healthcare delivery.