Across the cohort, there was no significant difference in the level of RBD-specific IgA detected in the stool of healthy controls versus COVID-19 patients (p = 0.48, Mann–Whitney test; Fig. 5C), nor in the total amount of fecal IgA (p = 0.76, Mann–Whitney test; Fig. S4C). Here, CD79A is linked to COVID-19.