We estimated immunization program costs, financing, and funding gaps for sixteen vaccines among ninety-four low- and middle-income countries during the period 2011-30. Inputs were obtained from the Institute for Health Metrics and Evaluation, the 2020 Decade of Vaccine Economics costing analysis, the World Health Organization, Gavi, and the United Nations Children's Fund. We found a total funding gap of $38.4 billion between 2011 and 2030, with the cost of immunization delivery being the main driver (86 percent) of the funding gap. On average, government financing of vaccination programs steadily rises throughout the period. However, the decline in both Gavi and development assistance for health (DAH) financing anticipated between 2011 and 2030 outpaces the forecasted increases in domestic government immunization spending. Probabilistic sensitivity analysis was applied to both the costing and the scenario analyses to address uncertainty in the financing of vaccines and vaccine delivery. The results highlight a narrowing gap for vaccine acquisition but a growing gap for vaccine delivery, which emphasizes the critical need for resource mobilization and sustainable financial strategies for immunization programs at national and global levels, as well as a need to address the COVID-19 pandemic's potential effects on government financing for vaccines between 2021 and 2030.