Date Time Likelihood of severe and ‘long’ COVID may be established very early on following infection New research provides important insights into the role played by the immune system in preventing – and in some cases increasing the severity of – COVID-19 symptoms in patients. It also finds clues to why some people experience ‘long COVID’. Our evidence suggests that the journey to severe COVID-19 may be established immediately after infection, or at the latest around the time that they begin to show symptoms Paul Lyons Among the key findings, which have not yet been peer-reviewed, are: Individuals who have asymptomatic or mild disease show a robust immune response early on during infection.