Covid Vaccine-Induced Thrombosis & Thrombocytopaenia (VITT)
aka “Vaccine induced prothrombotic immune thrombocytopenia”, (VIPIT)
The benefits of receiving AstraZeneca Covid vaccination still far outweigh the risks of clot on average, but there are both age-related and exposure-related considerations for the individual patient in front of you. This syndrome is extremely rare(1). Click here to see these broken down in greater detail:
1. At the time of writing, Norway has reported a rate of 1 in every 25,000 doses, Germany reported 1 in 100,000 doses, while Europe’s overall figures are 1 in 210,000. The UK has reported about 1 in 500,000 doses. Specifically, 169 reported cases of cerebral venous sinus thrombosis (CVST) and 53 cases of splanchnic vein thrombosis were reported in 34 million vaccine recipients in the UK and European Economic Area as of time of writing (16/4/21).
Does your patient’s presentation raise any concern about VITT?
Cases usually present 4-28 days post vaccination with progressive thrombosis, in order of (extremely low) frequency:
Cerebral venous sinus thrombosis.
Splanchnic vein thrombosis
NB. Bleeding can be significant and unexpected, due to the associated thrombocytopaenia.
Given the above, symptoms of concern are:
persistent and severe headache
focal neurological symptoms
seizures, or blurred or double vision (suggesting CSVT or arterial stroke)
shortness of breath or chest pain (suggesting pulmonary embolism or acute coronary syndrome)
abdominal pain (suggesting portal vein thrombosis)
or limb swelling, redness, pallor, or coldness (suggesting deep vein thrombosis or acute limb ischemia).
Please note: Until VITT has been ruled out, anticoagulation with heparin (both unfractionated heparin and low molecular weight heparins) should not be given. Platelet transfusions should also not be given. If anticoagulation is necessary under risk/benefit considerations, use first line anticoagulants: direct oral anti-Xa inhibitors (e.g. rivaroxaban, apixaban, edoxaban)
Community workup of suspected VITT
See RCEM/RCP guidance here
1. Ask patient about their COVID-19 vaccine history and note the date that they received the doses
2. Draw and send a full blood count (FBC) and clotting tube (initially for the lab to HOLD for later testing if needed) from the patient. If you have missed your blood courier or are working OOH, please discuss with the Acute GP service
3a. If platelet count is greater than 150 x10^9/L, VITT is unlikely, please consider other causes for the symptoms
3b. If platelet count is equal or less than 150 x10^9 /L, AND their symptoms occur within 28 days after COVID-19 vaccination, such patients are considered a suspected case of VITT.
4. Suspected VITT patients need to be further evaluated with D-dimer and fibrinogen levels (which can be added on to the HOLD clotting tube) and interpreted in accordance with the RCEM guidance. Please discuss with the Acute GP service as these patients may need admitting or may be seen through the AGP clinic.
5. If D-dimer is >2000mcg/L or fibrinogen is low, the patient likely needs admission for further workup: blood films drawn to confirm thrombocytopenia, PF4 antibody assay (ELISA HIT assay), and imaging (e.g. CT or MRI)
Treatment of confirmed VITT with significant clots is under the haematologists, likely with an admission high dose intravenous immunoglobulins.
See EPH guidance here (for AGP access)