The sensitivity in serum samples, collected at a median of 24 days after onset of symptoms, detected by the Anti-SARS-CoV-2-ELISA IgG (Euroimmun), EDITM Novel Coronavirus COVID-19 IgG ELISA (Epitope Diagnostics), Liaison® SARS-CoV-2 S1/S2 IgG (Diasorin), SARS-CoV-2 IgG on the ArchitectTM i2000 (Abbott), and Elecsys® Anti-SARS-CoV-2 (IgM/IgA/IgG) on the cobasTM e801 (Roche) was 84.3%, 78.4%, 74.5%, 86.3%, and 88.2%, respectively. Here, CD40LG is linked to COVID-19.