A Stochastic Approach to Determine the Optimal Vaccine Vial Size

摘要

Vaccines are perishable products stored in vials that once punctured have to be used within a specified length of time. In this paper, the wastage resulting from such unused doses in punctured vials is referred as open-vial wastage. In developing countries, the objective of vaccine distribution centers planning for immunization sessions in particular rural areas is to maximize the number of vaccinated children, while minimizing purchase, holding and wastage costs, which are directly affected by the number of vaccine doses stored in a vial. Larger vial sizes not only result in lower purchase and storage costs per dose, but they also result in higher levels of open-vial wastage. On the other hand, a single-dose vial has no open-vial wastage, but it results in higher purchase and storage costs. This study suggests a modified periodic review (nQ,r) policy to compute the optimal vial size Q and reorder point r that minimize the total cost incurred at a vaccine distribution center of a two-echelon system. The main contribution of this paper is to propose a reorder policy for vaccine vials, considering that each vaccine vial is an inventory model in which placing an order is mapped with puncturing a new vial.