SDC1 and COVID-19: Consistent with SARS-CoV-2-specific IgA levels noted in unvaccinated and vaccinated COVID-19+, we detected more CD138+IgA+ cells in the lungs of COVID-19+ at baseline and in response to SARS-CoV-2-specific peptides [Figure 4H, Supplementary Figure S12, and Supplementary Video S1 (https://figshare.com/s/4791622c8dfcd89f0aea)].