Among the others (recently reviewd by Xie et al., 2021, [48]), BPIFB4 seems to be a valid prognostic marker for COVID-19 being its low circulating levels in SARS-CoV-2-positive individuals (with respect to LLIs and controls groups) that is further reduced in high-grade patients [49]. Here, BPIFB4 is linked to COVID-19.