Vaccine-induced immune thrombotic thrombocytopenia (VITT), also called thrombosis with thrombocytopenia syndrome (TTS) and vaccine-induced prothrombotic immune thrombocytopenia (VIPIT), is condition in which the body produces blood clots.
VITT was observed in a small number of people who received the ChAdOx1 CoV-19 vaccine (AstraZeneca, University of Oxford, and Serum Institute of India), as well as small number of individuals who received the Ad26.COV2.S vaccine (Janssen; Johnson & Johnson). Both vaccines are based on an adenoviral vector.
Is Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT) Fatal?
Vaccine-induced immune thrombotic thrombocytopenia is a potentially life-threatening disorder, but it appears to be rare. Among millions of people who have received the adenovirus vector vaccines, several hundred patients developed the condition.
- Vaccination still remains the most important measure to prevent COVID-19 and curb the pandemic. There is broad consensus among regulatory agencies and experts that the benefits of vaccination greatly outweigh potential risks of rare vaccine side effects such as VITT.
- Vaccine-induced immune thrombotic thrombocytopenia usually starts within 5 to 10 days post-vaccination, and cases are typically identified between 5 to 30 days post-vaccination.
Symptoms of vaccine-induced immune thrombotic thrombocytopenia depend on the part of the body in which the blood clot develops and may include:
- Cerebral veins and dural venous sinuses in the brain and cranial cavity
- New, persistent headache
- Vomiting
- Visual impairment
- Focal neurologic deficits or seizures
- Brain damage or disease (encephalopathy)
- Altered mental state
- Loss of memory and cognitive ability
- Subtle personality changes
- Inability to concentrate
- Lethargy
- Progressive loss of consciousness
- Veins that supply the digestive tract (splanchnic veins: splenic, portal, mesenteric)
- Severe abdominal pain
- Back pain
- Leg (deep vein thrombosis, or DVT)
- Lung (pulmonary embolism, or PE)
- Acute chest pain
- Shortness of breath
- Eyes
- Eye pain
- Double vision
- Vision loss
- Blood clot in the brain (ischemic stroke)
- Sudden onset focal neurologic deficit
- Encephalopathy
- Acute limb ischemia
- Pain
- No pulse
- Pale skin (pallor)
- Sensory or motor neurologic deficits
What Causes Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT)?
Two adenoviral vector-based vaccines have been associated with causing vaccine-induced immune thrombotic thrombocytopenia (VITT):
- ChAdOx1 nCoV-19 (AstraZeneca, University of Oxford, and Serum Institute of India)
- Ad26.COV2.S (Janssen; Johnson & Johnson)
Risk factors for VITT are unknown and may be skewed by the demographics of early vaccinated populations. Possible risk factors for developing VITT may include:
- Female sex
- The first wave of people to receive the vaccine were young female health care workers
- Females are slightly more prone than males to develop a related syndrome called heparin-induced thrombocytopenia
- Younger age (younger than 55 or 60 years)
- Initial reports appeared to suggest that individuals with VITT were younger but this may reflect the age of the initially vaccinated populations
- Cases in individuals over 60 years are emerging
How Is VITT Diagnosed?
Vaccine-induced immune thrombotic thrombocytopenia (VITT) may be suspected in people who develop symptoms of blood clots during an appropriate time frame following one of the implicated vaccines.
Testing to identify and locate blood clots depends on the area affected and may include:
- Cerebral veins and dural venous sinuses in the brain and cranial cavity
- Magnetic resonance venography
- Conventional angiography
- Brain magnetic resonance imaging (MRI)
- Veins that supply the digestive tract (splanchnic veins: splenic, portal, mesenteric)
- Computerized tomography (CT) scan with contrast
- Doppler ultrasound
- Leg (deep vein thrombosis, or DVT)
- Compression ultrasonography with Doppler
- Lung (pulmonary embolism, or PE)
- CT pulmonary angiography
- Ventilation/perfusion (V/Q) scan
- Eyes
- MRI
- Magnetic resonance venography
- Blood clot in the brain (ischemic stroke)
- Brain MRI and/or head CT
- CT or magnetic resonance angiography of the head and neck
- Acute limb ischemia
- CT angiography
- Catheter-based angiography
Blood tests may include:
- Complete blood count (CBC) with platelet count
- Anti-PF4 antibody testing
- ELISA
- Functional assay
- Coagulation testing
- Prothrombin time (PT)
- Activated partial thromboplastin time (aPTT)
- Fibrinogen
- D-dimer
What Is the Treatment for VITT?
Vaccine-induced immune thrombotic thrombocytopenia (VITT) is potentially life-threatening.
Hospitalization is needed for many patients due to the severity of the condition and the potentially serious complications of blood clots.
Treatment for VITT may include:
- Anticoagulant medications
- Direct oral anticoagulants (DOACs)
- Factor Xa inhibitor (apixaban, edoxaban, or rivaroxaban
- Direct thrombin inhibitor (dabigatran)
- Direct oral anticoagulants (DOACs)
- Fondaparinux
- A parenteral direct thrombin inhibitor (argatroban or bivalirudin)
- High-dose intravenous immune globulin (IVIG)
- Recommended along with anticoagulation
- Therapeutic plasma exchange (TPE) and immunosuppression
- For disease that does not respond to treatment or disease with concerning features such as cerebral vein thrombosis (CVT) or multiple blood clots with evidence of excessive platelet activation
- Platelet transfusions
- Usually reserved for critical bleeding
- Management of bleeding
- Clinical monitoring for signs of thrombosis
- Platelet count monitoring
- Coagulation studies (prothrombin time [PT], aPTT, fibrinogen, D-dimer)
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https://www.ninds.nih.gov/Disorders/All-Disorders/Encephalopathy-Information-Page