Dynamically optimizing the administration of vaccines from multi-dose vials

Abstract

Many vaccines are manufactured in large, multi-dose vials that once opened, must be used within a matter of hours. As a result, clinicians (especially those in remote locations) face difficult tradeoffs between opening a vial to satisfy a potentially small immediate demand versus retaining the vial to satisfy a potentially large future demand. This article formulates a Markov decision process model that determines when to conserve vials as a function of time of day, the current vial inventory, and the remaining clinic-days until the next replenishment. The objective is to minimize open-vial waste while administering as many vaccinations as possible. It is analytically established that the optimal policy is of a threshold type. Furthermore, an extensive sensitivity analysis is conducted that speaks to the benefits of consolidating demand, investing in buffer stock, and adopting different vial sizes. Lastly, a practical heuristic is evaluated and shown to perform competitively with the optimal policy.

Keywords:

• Markov decision process
• perishable inventory model
• multi-dose vial
• vaccine wastage