Letter by Brambilla et al Regarding Article, "Patients With COVID-19 Have Elevated Levels of Circulating Extracellular Vesicle Tissue Factor Activity That Is Associated With Severity and Mortality—Brief Report". Issue 6 (27th May 2021) - Brambilla, Marta; Canzano, Paola; Becchetti, Alessia; Tremoli, Elena; Camera, Marina