Research On Prepositioning Strategy And Allocation Of Medical Supplies Under Public Health Emergencies

From the end of 2019 to the beginning of 2020,there was a lack of medical supplies and unreasonable allocation in the early stage of the outbreak of the new coronavirus pneumonia(COVID-19).It indicates shortcomings and deficiencies in both the stockpiling of medical supplies at the strategic level and the distribution at the operational level,all of which are needed to better respond to public health emergencies.Since public health events such as the COVID-19 epidemic are sudden,physical reserves are necessary to cover the demand for medical supplies in the initial stage of public health emergencies.Nevertheless,medical supplies are so time-sensitive that a stockpile of them may face the risk of expiration and deterioration.After all,public health emergencies such as the COVID-19 epidemic may last for a long time.Without sufficient contract reserves or production capacity reserves,it will be difficult to meet the long-term demand.Therefore,prepositioning strategy at the strategic level and allocation at the operational level are important to ensure uninterrupted supply to respond to public health emergencies and to avoid the potential waste of large physical reserves due to the uncertainty in duration.According to the characteristics of public health emergencies: suddenness and uncertainty in duration,this dissertation systematically studies the prepositioning and allocation of medical supplies.This work involves prepositioning strategy in the pre-event stage to prevent emergencies,and an allocation plan in the aftermath of their outbreaks to control them.Research is carried out from three aspects: the optimal allocation of physical reserves of limited medical materials,the joint optimization of prepositioning and allocation of physical medical supplies,and the joint optimization of prepositioning and allocation of physical medical supplies based on multiple various supply channels.Both the priority of the demand node and the supplementary role of medical materials donated by the society are incorporated into the allocation of medical supplies in the post-event stage.Considering the uncertainty in demand and donated supplies,a two-stage stochastic program is proposed to determine the allocation of limited medical supplies.The decisions are to allocate limited physical supplies in the storage pool in the first stage,and to allocate donated supplies in the second stage.The recourse function is calculated based on these decisions.Regarding the joint optimization of prepositioning at the strategic level and allocation of physical medical supplies at the operational level,the case of a single type is firstly studied.The problem is formulated as a two-stage stochastic program considering the capacity limitation.The objective is to minimize the total cost which is consist of storage cost in the pre-event stage and shortage cost in the post-event stage.Since there exists a polynomial algorithm for the corresponding mathematical model,this problem is an easy problem and Gurobi is employed to solve it.Then,the case of multiple types,that is,various medical supplies share storage space,is studied.Demand for medical supplies follows a uniform distribution and a stochastic programming approach is employed to model this problem.The structure of the model is further analyzed to derive the analytical expression of the optimal solution.It is difficult to meet the long-term and continuous needs of public health emergencies simply by physical reserves.Additionally,excessive physical reserves may cause huge waste since medical supplies are time-sensitive and the duration of public health emergencies is uncertain.The prepositioning and allocation of multiple types of medical supplies are studied.At the strategic level,various supply channels such as physical reserve,contract reserve and production capacity reserve are considered at the same time.At the operational level,medical supplies from different channels are involved.A two-stage stochastic programming model is established with to minimize the sum of the fixed costs of various reserve models,the procurement cost of physical reserves,and the expected loss after the event occurs.Considering the large scale of practical problems,many integer variables,and high requirements for solution accuracy,the Branch and Benders cut exact algorithm is designed based on the Branch and cut algorithm framework and the idea of generating cut planes with the Benders decomposition algorithm.Numerical experiments are carried out to verify the superiority of the algorithm in three aspects: solution time,solution stability and memory occupancy.A realistic and typical case study(inspired by the COVID-19 pandemic in Wuhan,China),considering the perishability of medical supplies,and the suddenness and uncertainty in the duration of public health emergencies,is used to verify the effectiveness and efficiency of this work.The results show that the reserve strategy based on a physical reserve can effectively respond to the suddenness of public health emergencies;the reserve strategy based on multiple supply channels,which effectively deals with the uncertainty of the duration,can simultaneously ensure the flexibility of supply chain of medical supplies,reduce the loss of stock-out and improve the utilization of physical reserves.These findings provide a theoretical framework to improve the system for responding to public health emergencies and providing emergency supplies.