FURIN and COVID-19: Nonetheless, we found anti-CoV antibodies in plasma of a COVID-19 patient after prolonged hospitalization and intensive care that targeted largely the same structurally conserved and functionally important regions of the viral N and S proteins (Supplemental Figure 8) as those that we detected in a sizable proportion of children, including antibodies binding to the highly conserved motif and furin-like S2′ cleavage site (R ̄SA[I/L]ED[I/L]LF), which provides further evidence for the clinical benefit of using convalescent plasma for the prevention and treatment of COVID-19 (65, 70, 71).