Illinois transmission modeling reveals that COVID-19 vaccination among people under 65 significantly reduces deaths in older adults through indirect protection. Using statewide survey data and contact patterns across age groups, researchers simulated scenarios where younger populations remained unvaccinated and found substantially higher mortality rates among the elderly compared to current vaccination coverage. This demonstrates herd immunity effects where vaccination in lower-risk groups creates protective barriers for vulnerable populations. The finding challenges current policy discussions about restricting COVID vaccines to only high-risk older adults. While older populations derive the greatest direct benefit from vaccination due to higher severe outcome risks, the modeling suggests such age-restricted approaches could paradoxically worsen outcomes for the very group they aim to protect. However, this preprint awaits peer review, and the modeling assumptions about contact patterns and transmission dynamics may not fully capture real-world complexity. The Illinois-specific data may also limit generalizability to other regions with different demographics or social mixing patterns. This represents confirmatory evidence supporting broader vaccination strategies over age-restricted approaches for maintaining population-level protection.