CD63 and COVID-19: There was a clear positive shift of the LEV histogram when compared to the histogram corresponding to SEVs as shown in Fig. 2A. This data suggests that the mean fluorescent intensity (MFI) of both markers for LEVs were significantly increased (CD63, p = 0.001; CD81, p = 0.023) in COVID-19 (+) patients compared to healthy donor samples (Fig. S5A, B).