This study aimed to conduct an economic analysis of the transition of the conventional vaccine supply and logistics systems to the vendor managed inventory (VMI) system in Thailand. Study design: Cost analysis of health care program. Methods: An ingredients based approach was used to design the survey and collect data for an economic analysis of the immunization supply and logistics systems covering procurement, storage and distribution of vaccines from the central level to the lowest level of vaccine administration facility. Costs were presented in 2010 US dollar. Results: The total cost of the vaccination program including cost of vaccine procured and logistics under the conventional system was US 0.60 per packed volume procured (cm3) and US 1.35 per dose procured compared to US 0.66 per packed volume procured (cm3) and US 1.43 per dose procured under the VMI system. However, the findings revealed that the transition to the VMI system and outsourcing of the supply chain system reduced the cost of immunization program at US 6.6 million per year because of reduction of un-opened vaccine wastage. Conclusions: The findings demonstrated that the new supply chain system would result in efficiency improvement and potential savings to the immunization program compared to the conventional system.