IL6 and acute respiratory distress syndrome: The two main reasons why the analysis of HE4 came to focus as a relevant biomarker in severe SARS-CoV-2 infection were that (i) ARDS has a fibroproliferative phase in its subacute stage when profibrotic mediators are produced at a higher quantity [25], and (ii) in SARS-CoV-2 ARDS, there is a protease-anti-protease imbalance in the airways causing elevated expression of the major serine protease inhibitor alpha1-antitypsin induced by IL-6 [26].