Although we found no differences in fecal secretory IgA levels between the patients and the controls, we observed some moderate–strong inverse correlations with some differentially increased taxa in COVID-19, including Bacillota (formerly Firmicutes) (r = 0.54; p = 0.035), Prevotellaceae (r = −0.62; p = 0.017), Schaalia (r = −0.83; p < 0.001), Granulicatella (r = −0.65; p = 0.013), Actinomyces (r = −0.55; p = 0.035), Ihubacter (r = −0.53; p = 0.038), and Collinsella (r = −0.51; p = 0.045). The gene discussed is CD79A; the disease is COVID-19.