CD79A and cytomegalovirus infection: In addition, infectious diseases such as cytomegalovirus, rubella, toxoplasmosis, and Epstein Barr virus are also considered to cause secretory IgA deficiency.(13) Recently, we reported a severe case of COVID-19 infection complicated with cytomegalovirus infection.(14) Third, epidemiologic studies of selective IgA deficiency have revealed that recurrent respiratory infections are the most common.(10) To the best of our knowledge, so far, no detailed information is available on secretory IgA with regards to COVID-19.