No Extra Blood Clot Risk After Second Dose of AstraZeneca Covid Vaccine: Study

The AstraZeneca COVID-19 vaccine is associated with a small risk of rare blood clots after the first dose, and no extra risk after the second shot, according to a study led and funded by the British-Swedish drugmaker. The research, published in The Lancet on Tuesday, shows that the rates of

The AstraZeneca COVID-19 vaccine is associated with a small risk of rare blood clots after the first dose, and no extra risk after the second shot, according to a study led and funded by the British-Swedish drugmaker. The research, published in The Lancet on Tuesday, shows that the rates of the very rare clotting disorder, thrombosis with thrombocytopenia syndrome (TTS), following a second dose of the vaccine are comparable to those among unvaccinated population.

TTS is a very rare syndrome which occurs when a person has blood clots (thrombosis) as well as low platelet counts (thrombocytopenia). It is also referred to as vaccine-induced immune thrombotic thrombocytopenia (VITT).

Rare cases of TTS have been reported after immunisation with the AstraZeneca vaccine, known as Covishield in India, which led to several countries restricting or stopping the use of the preventive.

The authors demonstrated that the estimated rate of TTS following a second dose of AstraZeneca was 2.3 per million vaccinees, comparable to the rate observed in an unvaccinated population.

The AstraZeneca COVID-19 vaccine is associated with a small risk of rare blood clots after the first dose, and no extra risk after the second shot, according to a study led and funded by the British-Swedish drugmaker. The research, published in The Lancet on Tuesday, shows that the rates of the very rare clotting disorder, thrombosis with thrombocytopenia syndrome (TTS), following a second dose of the vaccine are comparable to those among unvaccinated population.

TTS is a very rare syndrome which occurs when a person has blood clots (thrombosis) as well as low platelet counts (thrombocytopenia). It is also referred to as vaccine-induced immune thrombotic thrombocytopenia (VITT).

Rare cases of TTS have been reported after immunisation with the AstraZeneca vaccine, known as Covishield in India, which led to several countries restricting or stopping the use of the preventive.

The authors demonstrated that the estimated rate of TTS following a second dose of AstraZeneca was 2.3 per million vaccinees, comparable to the rate observed in an unvaccinated population.

Co-developed by the University of Oxford, the AstraZeneca vaccine is based on a weakened version of a common cold virus (adenovirus) that causes infections in chimpanzees. The preventive contains the genetic material of the SARS-CoV-2 virus spike protein, which the virus uses to enter and infect the human cells.

After vaccination, the surface spike protein is produced, priming the immune system to attack the SARS-CoV-2 virus if it later infects the body. According to its manufacturers, the AstraZeneca vaccine has been granted emergency use in more than 80 countries across six continents.

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