PF4 and Thrombocytopenia: Patients who experienced SVT post-COVID-19 vaccination were more likely to have thrombocytopenia (n = 14) [47, 48, 50, 60], positive for antibodies directed against platelet factor 4 antibodies (n = 13) [48, 50, 60], high D-dimer (n = 10) [47, 48, 50, 60], high activated partial thromboplastin time (n = 6) [50, 60], high international normalized ratio (n = 5) [60], and low fibrinogen (n = 5) [50, 60].