As per the study published in “The New England Journal of Medicine”,  a pathogenic PF4-dependent syndrome, not associated with the usage of heparin therapy, may occur after vaccination with ChAdOx1 nCoV-19. This study reported findings in 23 individuals who presented with thrombocytopenia and thrombosis six to 24 days after getting the initial dosage of the ChAdOx1 nCoV-19 vaccine. Based on their clinical and laboratory findings, investigators detected a new underlying mechanism.

In the absence of prior prothrombotic medical conditions, 22 participants presented with acute thrombocytopenia and thrombosis, majorly cerebral venous thrombosis, and one subject presented with hemorrhagic phenotype and isolated thrombocytopenia. At presentation, all the participants were found to have normal or low fibrinogen levels and raised levels of d-dimer. No evidence of causative precipitants or thrombophilia was detected.

The testing for antibodies to PF4 was found to be negative in one subject while it was found to be positive in 22 patients (with one equivocal result). Vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains crucial for controlling the coronavirus disease 2019 (COVID-19) pandemic. Prompt detection of this rare syndrome is essential due to the therapeutic implications linked with it.

Based on the pathophysiological features witnessed in these patients, it is suggested that platelet transfusions therapy should not be used due to the risk of advancement in thrombotic symptoms. For the initial incidence of the symptoms, the administration of intravenous immune globulin and nonheparin anticoagulant agent should be taken into consideration.