In agreement with our findings with the earlier cohort of 81 symptomatic individuals with COVID-19, the SFB assay detected IgM (Figure 3A), IgA (Figure 3B), IgG (Figure 3C) and IgG subclasses (Figures 3D–3G) against the S protein in PCR-positive and symptomatic infections. Here, CD40LG is linked to infection.