A Case of X-Linked Agammaglobulinemia and COVID-19 in a Japanese Infant.

An infant was diagnosed as having X-linked agammaglobulinemia (XLA) at age 3 months and was receiving immunoglobulin replacement therapy. He developed SARS-CoV-2 infection at age 7 months and was treated with intravenous immunoglobulin, remdesivir, and dexamethasone. His respiratory symptoms improved quickly, and the infection resolved. Viral disappearance was confirmed via PCR, and the result of a SARS-CoV-2 test was negative on day 67 of illness, as a result of antiviral therapy. Immunoglobulin administered to the patient did not contain anti-SARS-CoV-2 antibodies, and no seroconversion of anti-SARS-CoV-2 antibodies was observed after healing. These findings suggest that humoral immunity did not contribute to infection in our patient. Thus, the importance of cellular immunity against COVID-19 was confirmed. In the future, it is hoped that testing companies will be able to use the ELISPOT assay to check cellular immunity in order to confirm the effectiveness of vaccines and the history of infection.