Hence, VITT is definitively diagnosed if all of the following five criteria are fulfilled: (1) onset of symptoms five to thirty days following COVID-19 vaccination, (2) verified acute thrombosis or severe persistent headache, (3) platelets below 150 × 109/L, (4) D-Dimer levels more than 4000 fibrinogen equivalent units (and more than eight times the upper limit of the normal), and (5) a positive ELISA assay for antibodies against PF4/heparin. The gene discussed is PF4; the disease is COVID-19.