A U.S. modeling analysis projects that delayed hepatitis B vaccination policies would increase chronic infections acquired by age 20 relative to universal vaccination at birth. The study forecasts a 19% increase with delayed vaccination and an 83% increase under shared-decision policies. The model size—built on population-scale birth cohorts—frames infant vaccination timing as a key determinant of later lifelong infection risk. It underscores the potential consequences of adopting more conditional or delayed approaches to hepatitis B immunization. While the findings are model-based rather than direct trial outcomes, the magnitude and direction of effect provide actionable planning implications for public health decision-making and vaccine rollout design.