MMP9 and COVID-19: In addition, using the same design, we also analyzed the evolutionary changes over time of proteins of the neurovascular unit as a biomarker of BBB disruption: proteins of the extracellular matrix (PPIA and MMP-9), astrocytes (S100β and GFAP), and neurons (NfL) were detectable in blood samples from COVID-19 patients in the acute phase, and in the subsequent phases, they were reduced until they reach the control levels, suggesting that the initial leakage of BBB seems to be restored during the next 6 months.