Comparison of quantitative total IgG, IgM, and IgA antibody response to the SARS-CoV-2 RBD and N proteins using Bio-Plex and Meso Scale assays. Total IgG, IgM, and IgA antibody levels were assayed in sera by both the Bio-Plex and MSD platforms for 304 participants with COVID-19 in ACTIV-2/A5401 at entry (pre-treatment). Here, CD40LG is linked to COVID-19.