The fields of public-health and infectious-disease research have revealed much about the effects of pandemics and how to curb them. This year, a large volume of work on COVID-19 has illuminated the behaviour of both the virus and the disease. Research has also revealed uncertainties, gaps and errors in our knowledge, as would be expected. But that doesn’t excuse the behaviour we are seeing from politicians around the world, exemplified by Trump’s notorious actions: a chaotic, often ill-informed response, with scientists being attacked and undermined.