Introduction. The ongoing war in Ukraine has severely disrupted the health system, with repeated attacks on energy and health infrastructure, as well as damage to transport routes, posing a major threat to maintaining the vaccine cold chain. In this context, the authorities, along with WHO, took action to strengthen the preparedness of subnational vaccine stores to effectively respond to emergencies and minimize the risk of temperature excursions during vaccine storage and transportation.

Context: Ukraine’s vaccine cold chain operates through 25 newly established subnational vaccine stores. These facilities play a critical role in storing and distributing vaccines to lower levels of the health system. Following recent modernization, most stores use WHO-prequalified cold chain equipment, remote temperature monitoring, power backup systems, and specialized vehicles. However, the ongoing conflict exposes them to frequent disruptions in power, logistics, and communications.ApproachTo address this need, we co-created on-site functional simulation exercises. The 7-h programme combined a locally led risk analysis with three progressively complex simulated emergencies, testing responses to equipment failure, prolonged power outages, and transport incidents.Implementation experienceBetween July and November 2025, simulation exercises were conducted in 18 oblasts, revealing recurring gaps in alert systems, backup storage and transport capacity, procedures implementation, and staff training. After the exercises, each store developed a tailored action plan to address these. Participant feedback indicated improved technical readiness, clearer roles and responsibilities.Lessons learned

Co-created, on-site simulation exercises proved effective and cost-efficient for enhancing cold chain preparedness, offering a replicable model for other public health functions in conflict settings.