To investigate the specificity of the ELISA assays we included 54 serum samples that were collected before the COVID‐19 pandemic or from patients testing negative for COVID‐19 but confirmed with other bacterial, viral infections or autoimmune diseases. These samples had been stored frozen at −70°C. The samples included sera testing positive for Epstein‐Barr virus (n = 1), Cytomegalovirus (n = 4), Influenza A (n = 5), Influenza B (n = 6), Parainfluenza virus (n = 9), Mycoplasma pneumoniae (n = 3), Respiratory syncytial virus (n = 3), Borrelia burgdorferi (n = 6), Human granulocytic anaplasmosis (HGA) (n = 3), Treponema pallidum (n = 1), Rheumatoid arthritis (n = 3), Systemic lupus erythematosus (n = 1). Additionally, nine sera samples were obtained from patients with PCR‐confirmed human coronavirus infections, not SARS‐CoV‐2.