To better understand the role of type I IFN in the evolution of COVID-19, we performed a longitudinal study of blood IFN-α2 levels in 140 patients from the CORIMUNO-19 cohort (NCT04324047) divided into two groups, group 1: patients with severe COVID-19 requiring at least 3L/min of oxygen (n=81) and group 2: patients with critical COVID-19, requiring high-flow, non-invasive (NIV) or mechanical ventilation (MV) in intensive care unit (ICU) (n=59) (25). Here, IFNA2 is linked to COVID-19.