Frequency of SARS-CoV-2 antecedent infection in patients with Kawasaki disease.

Since the COVID-19 pandemic, it has been found that SARS-CoV-2 antecedent infection can cause multisystem inflammatory syndrome in children. However, the frequency of SARS-CoV-2 antecedent infection in Kawasaki disease (KD) is unknown. The purpose of this study was to investigate the frequency of SARS-CoV-2 infection that preceded the onset of KD. This study is a multi-center observational study. The subjects were patients who were diagnosed with KD at 4 hospitals from April 1, 2020 to August 31, 2022. Serum SARS-CoV-2 IgM and total antibody including IgG levels were measured by the chemiluminescence immunoassay method before and after treatment for KD. A total of 55 patients participated in the study. The first antibody measurement before the initial treatment was performed on a median of 4th days of illness and the second antibody measurement was performed after the initial treatment on a median of 12th days of illness. No patient had a significant increase in SARS-CoV-2 IgM levels in two measurements. Only one patient (1.8%) had elevated total antibodies including IgG, and the patient had a history of COVID-19 6 months before the onset of KD. SARS-CoV-2 antecedent infection before the onset of KD was not observed in this study, and strong association between development of KD and SARS-CoV-2 infection was not suggested.