At the admission time, we found a higher frequency of the PMN-MDSC cell population (identified as Lin−, HLA-DR−, CD11b+, CD33+, CD15+, CD14−; Fig. 1A) in 128 hospitalized COVID-19 patients requiring or not requiring intensive care unit (ICU) compared to HD (Fig. 1B). The gene discussed is CD33; the disease is COVID-19.