Multi-dose vial administration with non-stationary demand and delayed service

Abstract

To vaccinate patients arriving to clinics in remote locations, clinicians reconstitute vials containing multiple doses of lyophilized vaccines, but often only partially use the vials by the end of the vaccination session. The unused doses are discarded and termed “open vial waste”. Current practice is typically to vaccinate all patients as long as there is inventory on-hand, which results in significant open vial waste. Previous work on determining dynamic vaccine administration policies to minimize open vial waste makes the simplifying assumptions that unvaccinated customers are lost and that the arrival rate is both unaffected by the administration policy and constant throughout the replenishment cycle. We relax these assumptions by considering a positive probability of return for unvaccinated patients and by incorporating non-stationary arrival rates throughout the replenishment cycle as well as within each session. To study the impact of these enhancements, we perform extensive numerical experiments at the clinic level for a single replenishment cycle and then extrapolate to multiple clinics and the worldwide system on an annual basis. The results indicate potential savings on the order of millions of doses per year.