COVID-19, an advance which may help identify those at high risk of dying from the disease, and suggest drugs to treat them.The researchers from Yale University in the US examined 113 patients admitted to the Yale New Haven Hospital, and analysed the varying immune system responses they exhibited during their hospital stay, from admittance to discharge, or death.The study, published in the journal Nature, found that all patients shared a common COVID-19 "signature" in immune system activity early in the course of disease.However, those who experienced only moderate symptoms exhibited diminishing immune system responses and viral particle levels in their bodies over time, the researchers said."This study shows how people's immune system.