PF4 and COVID-19: The prevailing diagnostic criteria proposed by experts indicate that a diagnosis of VITT should be made if all five of the following are met: (i) venous or arterial thrombosis, (ii) thrombocytopenia, (iii) occurring between 4 to 30 or 42 days after receiving the COVID-19 vaccine, (iv) presence of antibodies against PF4, and (v) markedly elevated D-dimer [14,15].