Applying economics to vaccine delivery can save money and lives. With better analytical knowledge and better skills in decision-analysis, decision makers can improve vaccination program sustainability, efficiency, and financial predictability, leading to overall improvement in health system allocative efficiency. This handbook is a practical and accessible guide to the theory, methods, and research of health economics applied to immunization, and an essential and timely addition to the series of Handbooks in Health Economic Evaluation. By bringing these principles of vaccines and economics together, it is a valuable resource for public health workers, healthcare practitioners, educators, students, researchers, decision makers, and all those working in the immunization field. The handbook guides readers through this critical subject, whether they are already versed in economics or new to the subject. The handbook includes practical examples relevant to high-, middle-, and low-income settings. It offers background information on vaccines and the vaccine landscape, with relevant reviews of vaccine financing, vaccine adoption, and scaling up vaccine delivery. The handbook's main chapters are on principles, costing, economic evaluation, advanced methods, and financing and resource tracking. Summarizing both theory and applications, it is suitable for self-learning and for training and courses. Links to online exercises and resources will help readers learn and apply key insights.