Why is it in the News?

Global pharmaceutical giant AstraZeneca has said that its AZD1222 vaccine against Covid-19, which was made under license in India as Covishield, could cause low platelet counts and formation of blood clots in “very rare” cases.

What is Thrombosis with Thrombocytopenia Syndrome (TTS)?

• Thrombosis with Thrombocytopenia Syndrome (TTS) is characterised by thrombosis formation (blood clots) combined with thrombocytopenia (low platelet count) with symptoms typically presenting in the 4-42 days after vaccination.
  • Platelets are small cells that help blood to clot, so having too few of them can be dangerous.
• It often involves unusual blood clot locations, such as in the brain (cerebral venous sinus thrombosis) or abdomen.
  • The condition was observed in people who received adenoviral vector COVID-19 vaccines, such as Vaxzevria, Covishield (AstraZeneca), and the Johnson & Johnson/Janssen COVID-19 vaccine.
• TTS seems to occur because the body's immune system reacts to the vaccine by making antibodies that attack a protein involved in blood clotting.
• According to the Centers for Disease Control (CDC), TTS is classified into 2 tiers based on the location of thrombosis and severity of symptoms.

Tier 1:

• Rare blood clots, like in the brain or gut, sometimes alongside more typical ones in the legs or lungs.
• Low platelet count (below 150,000 per microliter).
• Positive anti-PF4 ELISA tests can help confirm diagnosis but aren't always needed.
• Tier 1 cases are usually more severe and riskier.
• This is more common in younger people.

Tier 2:

• Common blood clots, like in the legs or lungs.
• Low platelet count (below 150,000 per microliter).
• A positive anti-PF4 ELISA test is necessary for diagnosis.

Symptoms of TTS:

• Symptoms of TTS can include severe headaches, stomach pain, swelling in the legs, trouble breathing, and problems with thinking or seizures.