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Vaccine-induced immune thrombotic thrombocytopenia

Key sources
The following summarized guidelines for the evaluation and management of vaccine-induced immune thrombotic thrombocytopenia are prepared by our editorial team based on guidelines from the World Health Organization (WHO 2023) and the American Society of Hematology (ASH 2022).


1.Screening and diagnosis

Diagnostic criteria: diagnose VITT if all 5 criteria are MET:
COVID-19 vaccine 4-42 days before symptom onset
any venous or arterial thrombosis (often cerebral or abdominal)
thrombocytopenia (platelet count < 150×10⁹/L)
positive PF4 ELISA (heparin-induced thrombocytopenia assay)
markedly elevated D-dimer (> 4 times the ULN)
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  • Differential diagnosis

2.Classification and risk stratification

Vaccine-related risks: recognize that the incidence of VITT is extremely low, and the risk of death and serious outcome of COVID-19 infection, including thrombosis, far outweigh the risk of VITT possibly associated with highly efficacious vaccines.

3.Diagnostic investigations

Laboratory tests: obtain urgent evaluation for VITT if any of the following develop 4-30 days after vaccination:
severe headache
visual changes
abdominal pain
nausea and vomiting
back pain
shortness of breath
leg pain or swelling
petechiae, easy bruising, or bleeding
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  • Diagnostic imaging

4.Medical management

Anticoagulation and IVIG
As per WHO 2023 guidelines:
Initiate anticoagulation in all patients presenting with VITT following COVID-19 vaccination.
Initiate IVIGs or non-heparin-based anticoagulants in patients with VITT following COVID-19 vaccination,
Consider initiating heparin for anticoagulation if non-heparin anticoagulants are not available.

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  • Corticosteroids

  • Aspirin

5.Therapeutic procedures

Platelet transfusion: as per WHO 2023 guidelines, do not administer platelet transfusion in patients presenting with VITT following COVID-19 vaccination unless in emergency situations when surgery is required, thrombocytopenia is severe (< 50×10⁹ platelets/L), and the patient is bleeding, or platelet transfusion is required to be able to proceed with emergency surgery.

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  • Plasma exchange

6.Follow-up and surveillance

Indications for referral
Obtain urgent consultation with a hematologist with expertise in hemostasis for patients with thrombocytopenia or thrombosis. Avoid using heparin until VITT has been excluded or until an alternative other plausible diagnosis has been made.
Consider referring patients with confirmed VITT to a tertiary care center.