This study examines the use of epidemiological modelling to policymakers in Covid-19 outbreak response. Prior to Covid-19, there was little readiness of global health systems and many science-policy networks were assembled ad-hoc. Moreover, in the field of epidemiological modelling, one with significant sudden influence, there is still no international guidance or standard of practice on how modelled evidence should guide policy during major health crises. Here we use a multi-country case study on the use of epidemiological modelling in emergency Covid-19 response, to examine the effective organisation of crisis science-and-policy at different scales. We investigate Covid-19 modelling-policy systems and practices in 13 different countries, spanning all six UN geographic regions. Data collection takes the form of expert interviews with a range of national decision makers, scientific advisors, and modellers. We examine the use and organisation of modelling in health policy on a global scale, introducing a classification framework for modelling-policy systems and recommendations for future practice. Full analysis and interpretation of the breadth of interview responses is presented, providing evidence for the current and future use of modelling in health crises. We argue that long-standing relationships are fundamental to effective science-to-policy pathways and outline activities that scientists and policy actors could action in their own countries. This article serves as a first evidence base for the current use of modelling in a recent major health crisis.
