Consistent with the observed increased levels of monocyte activation–associated biomarkers, and in agreement with recent reports (26, 27), peripheral blood monocytes of COVID-19 patients exhibited extensive vacuolization (Supplemental Figure 5A), and the MFIs of CD169, and of CD63, CD11b, and b558, were greater in peripheral blood CD14+ monocytes of COVID-19 patients (n = 2) relative to HVs (Supplemental Figure 6). Here, CD63 is linked to COVID-19.