CD40LG and infection: Participants with a first COVID-19 diagnosis based on a positive RT-PCR result for SARS-CoV-2 and clinical manifestation underwent serial blood collection for IgM and IgG antibody analysis on days 15, 30, 45, 60, and 90 (D15, D30, D45, D60, and D90), respectively, after the onset of symptoms of the first infection.