FCGR3B and COVID-19: Given the substantial differences in FcγR-binding properties across vaccinees who did or did not ultimately develop COVID-19, specifically related to differential FcγR3B- and FcγR2B-binding profiles, we generated plasma pools of equal numbers of vaccine samples that displayed discrete binding profiles to FcγR3B or FcγR2B (FcγR2B+FcγR3B− 57% versus 20% and FcγR2B−FcγR3B+ 10% versus 31%, for vaccinated COVID-19+ and vaccinated COVID-19−, respectively), for deeper antibody Fc-functional characterization (Fig. 5a).