FCGR2A and infection: Importantly, salivary antibodies from COVID-19–recovered vaccinees displayed higher FcγR engagement following 2 antigen exposures (1 × prior infection + 1 × BNT162b2) as compared with the vaccinated only cohort (2 × BNT162b2), also primarily against the conserved antigens S2 and ST (P ≤ 0.01) (Figure 2, B and C, and Supplemental Figure 3A).