Patent must meet all 5 of the following criteria:Onset of symptoms 5–30 days post SARS‐CoV‐2 vaccinationPresence of thrombosisMarked elevation of D‐dimer level (>400 mcg/L FEU)Thrombocytopenia (platelet count <150 × 109/L)Positive ELISA for anti‐PF4 antibodies. Here, PF4 is linked to Thrombocytopenia.