In severe samples, two CC clusters were observed one of which (TNF, IL17A, IL17F, IL9, IL2, and IL4) correlated positively with neutrophils and largely negatively with monocytes and lymphocytes, providing insight into inflammatory profiles associated with lymphopenia and neutrophilia occurring in severe COVID-19 (Henry et al., 2020; Terpos et al., 2020). Here, IL9 is linked to COVID-19.