IL-6 is well established as a biomarker for disease severity in COVID-1928–31 and as a predictor for adverse clinical outcomes including mortality,32–36 as well as for respiratory failure and the need for mechanical ventilation.37 IL-6 has been used as a prognostic biomarker in COVID-19-associated hyperinflammatory syndrome.38 In agreement with these studies, our results showed that IL-6 plasma levels at ICU admission were associated with disease severity in COVID-19 and were predictive of worse respiratory outcomes and mortality in ICU. Here, IL6 is linked to respiratory failure.