This is such a useful summary from Trisha Greenhalgh’s excellent Boston Review essay:
In relation to face coverings, for example, there was basic scientific evidence on how the virus behaves. There were service-level data from hospital and general practitioner records. There were detailed comparative data on the health system and policy responses of different countries. There were computer modeling studies. There was a wealth of anecdotal evidence (for example, one general practitioner reported deaths of 125 patients across a handful of residential care homes). But for the UK government’s Scientific Advisory Group for Emergencies (SAGE), whose raison d’être is “ensuring that timely and coordinated scientific advice is made available to decision makers,” this evidence carried little weight against the absence of a particular kind of evidence—from randomized controlled trials and other so-called “robust” designs.
https://bostonreview.net/science-nature/trisha-greenhalgh-will-evidence-based-medicine-survive-covid-19
Mark Carrigan 