Studies on the side effects of the ChAdOx1 nCOV‐19 vaccine suggested that it can induce an immune reaction similar to that of heparin‐induced thrombocytopenia (HIT) by producing autoantibodies to PF4–polyanion complex, which activates the platelets, thus, causing thrombosis and thrombocytopenia.5 The gene discussed is PF4; the disease is deep vein thrombosis.