The AstraZeneca COVID-19 vaccine, developed in collaboration with Oxford University and sold as Covishield in India and Vaxzevria in Europe, has been linked to an increased risk of Vaccine-Induced Immune Thrombocytopenia and Thrombosis (VITT), a rare but potentially fatal blood clotting disorder. Researchers announced these findings, noting that VITT emerged as a new disease during the height of the COVID-19 pandemic in 2021, associated with adenovirus vector-based vaccines.
What Is Vaccine-Induced Immune Thrombocytopenia and Thrombosis?
According to the American Society of Haematology, VITT is caused by an unusually dangerous blood autoantibody directed against a protein called platelet factor 4 (PF4). Separate studies in 2023 by scientists from Canada, North America, Germany, and Italy identified a similar disorder with the same PF4 antibody following natural adenovirus (common cold) infections, which was fatal in some cases.
Recent research from Flinders University in Australia and international experts discovered that the PF4 antibodies in both adenovirus infection-associated VITT and classic adenoviral vector VITT share identical molecular signatures. Professor Tom Gordon from Flinders University highlighted that these findings indicate that the pathways of lethal antibody production in these disorders are virtually identical and have similar genetic risk factors.
These insights have significant clinical implications, suggesting that lessons learned from VITT could apply to rare cases of blood clotting after adenovirus infections. Moreover, these findings could impact future vaccine development.
Vaccine-Induced Immune Thrombocytopenia and Thrombosis Symptoms
Thrombosis refers to the formation of blood clots within blood vessels, which can impede blood flow and cause serious complications. Society of Critical Care Medicine shared that the symptoms of thrombosis can vary depending on the location of the clot:
- Severe headache
- Blurred vision
- Seizures
- Stroke-like symptoms (e.g., difficulty speaking, weakness on one side of the body)
- Pain and swelling in one leg, usually the calf
- Red or discoloured skin on the leg
- A feeling of warmth in the affected leg
- Shortness of breath
- Chest pain, especially when breathing deeply
- Rapid or irregular heartbeat
- Coughing, sometimes with blood
- Pain and coldness in the limb
- Pale or blue-coloured skin
- Weak or absent pulse in the affected limb
When to Seek Medical Attention
If you or someone you know has received a COVID-19 vaccine and develops any of the above symptoms, it is crucial to seek medical attention immediately. Early diagnosis and treatment of VITT can significantly improve outcomes.
Here’s how VITT is treated:
- Anticoagulants: Medications to prevent further clotting. However, heparin (a common anticoagulant) is usually avoided due to the risk of exacerbating the condition.
- Intravenous Immunoglobulin (IVIG): Used to reduce the immune response against platelets.
- Corticosteroids: To reduce inflammation and modulate the immune system.
- Platelet Transfusions: In severe cases of thrombocytopenia, although generally avoided unless necessary due to the potential for worsening thrombosis.
VITT is a rare but serious condition that requires prompt medical attention. Understanding the symptoms of both thrombosis and thrombocytopenia can help ensure timely diagnosis and treatment. If you suspect VITT, contact healthcare professionals immediately to ensure appropriate care.
The current research follows AstraZeneca's legal acknowledgement in February that its COVID vaccine can, in very rare cases, cause Thrombotic Thrombocytopenic Syndrome (TTS), a rare side effect that leads to blood clots and a low platelet count. TTS has been linked to at least 81 deaths in the UK and hundreds of serious injuries. Consequently, AstraZeneca has voluntarily withdrawn the marketing authorisation for its COVID vaccine in Europe and other global markets.