S100A9 and Sepsis: Numerous studies have shown that S100A9 is upregulated in various inflammatory and infectious diseases, including sepsis and patients with severe COVID-19 infection (Chen et al., 2020a; Dubois et al., 2019; Holzinger et al., 2019; Liao et al., 2021; Marinkovic et al., 2020; Wang et al., 2014).