A technical support team including Agence de Médecine Préventive (AMP), the selleck screening library HERMES logistics modeling team, PATH, and Transaid worked with the Benin MOH to explore different potential redesigns of the Benin vaccine supply chain
and how they would compare with simply adding refrigerators and freezers to the current vaccine supply chain. This involved developing a detailed HERMES (highly extensible resource for modeling supply chains)—generated simulation model of the Benin vaccine supply chain which could serve as a “virtual laboratory” to test the effects of different changes  and . We developed a detailed, discrete-event simulation model of the Benin vaccine supply chain in our HERMES framework. Programed in Python, HERMES uses features provided by the SimPy package. Previous publications have described the structure of HERMES and HERMES-generated, country-specific models in detail , , , , , , , , , , ,  and . Our Benin model represents
an operational vaccine cold chain based on field data, with key physical components (e.g., every storage location, refrigerator, freezer, vaccine carrier, transport device, and vaccine vial) and dynamic processes (e.g., ordering, shipping, and vaccine administration) simulated over a one-year time interval with a warm-up period of six months. The model tracks each simulated vial as it travels through the supply chain and provides a FDA-approved Drug Library ic50 wide range of outputs, including the location and severity of each bottleneck due to inadequate storage or transport capacity, as well as wastage due to expiry of unopened vials or unused doses in an opened
multi-dose vial. Wasted doses are removed from the system and are taken into account when locations order vaccines. Once parameterized, the flow of vaccines through the system is simulated through dynamic interactions of ordering, storage, transport, and vaccination events. Demand for vaccines is modeled stochastically at each location through vaccination sessions drawing from a Poisson distribution around the Astemizole expected number of patients from yearly census estimates. This, in addition to stochastically scheduled events in the dynamic simulation, requires running each scenario over several iterations to gather average statistics for key metrics. Data collection tools were adapted from existing tools developed and utilized by Project Optimize to assess resource use and logistics costs of the national immunization program vaccine supply chain, tailored to incorporate the data needs for HERMES. The effective vaccine management (EVM) tool was adapted to collect additional data for the HERMES model, while the cold chain equipment management (CCEM) and stock management tool (SMT) further augmented model details. This included a questionnaire for each level of the supply chain to capture the resource use for the storage and distribution functions of the supply chain, as well as the stock movement data.