There was a clear association between the median bacterial loads in oropharyngeal swabs and serum IgA deficiency: median bacterial load increased gradually as patients were more profoundly IgA impaired (median±interquartile range IQR: HC 3.1 × 106 ± 38.4 × 106, CVID+IgA 15.0 × 106 ± 132.2 × 106, CVID-IgA 33.4 × 106 ± 154.3 × 106, XLA 50.5 × 106 ± 172.2 × 106 copies of the 16S rRNA gene). This evidence concerns the gene CD79A and selective IgA deficiency disease.