We have used this antigen to build three enzyme‐linked immunosorbent assays (ELISAs) that can detect IgM, IgG and IgA antibodies against SARS-CoV-2 and demonstrate here the performance of these assays using a large cohort of clinical samples from qRT-PCR positive COVID-19 patients and from individuals with no prior exposure to COVID-19. The gene discussed is CD40LG; the disease is COVID-19.