Inversely correlated classically secreted proteins include eight positive acute phase proteins (SERPINA3, SERPINA1, ITIH4, SAA2, SAA1, CP, ORM1, CD163); nine complement components (CPN1, C9, SERPING1, C6, CFHR5, CPN2, CFB, FCN2, C5); four coagulation proteins (F5, SERPINF2, F9, F11); and 21 immunoglobulin segments, including IGHV4‐34 and IGHV1‐69 that are found in autoantibodies and increased in children with multisystems inflammatory syndrome associated with COVID‐19 (Porritt et al., 2021; Supplementary Spreadsheet 1). This evidence concerns the gene C9 and COVID-19.