Relationship between Selective IgA Deficiency and COVID-19 Prognosis.

The prevalence and mortality rates of coronavirus disease 2019 (COVID-19) widely vary among populations. Mucosal immunity is the first barrier to the pathogen's entry into the body. Immunoglobulin A (IgA) is the primary antibody responsible for mucosal immunity. We explored the relationship between selective IgA deficiency (SIgAD) and COVID-19 severity. We included 424 patients (203 women) with COVID-19. Eleven patients had SIgAD. Laboratory data of patients with SIgAD and normal IgA levels were compared. The relationship between SIgAD and severe COVID-19 infection was explored using logistic regression analysis. In the univariate logistic regression analysis, the risk of severe COVID-19 disease in patients with SIgAD was approximately 7.7-fold higher than that in other patients (odds ratio [OR], 7.789; 95% confidence interval [CI], 1.665-36.690, P = 0.008), while it was 4-fold (OR, 4.053; 95% CI, 1.182-13.903, P = 0.026) higher in the multivariate logistic regression analysis. Serum IgA levels were positively correlated with total lymphocyte counts and negatively correlated with C-reactive protein levels, which was a risk factor for severe COVID-19. In patients with SIgAD, the number of severe acute respiratory coronaviruses 2 that pass through mucosal membranes may be increased, leading to complications such as cytokine storm syndrome and acute respiratory distress syndrome.