AstraZeneca's Covishield causes rare blood clot disorder TTS: What is it?

Covishield, a vaccine developed by AstraZeneca and Oxford University and manufactured by the Serum Institute of India, can, in rare instances, lead to TTS

AstraZeneca, the company that makes the Covishield vaccine for Covid-19 pandemic, has admitted the inoculation has potential side effects.

The company's admission, presented in a legal document before the High Court of Justice in London, conveys that the Covid vaccine can in extremely rare cases induce Thrombosis with Thrombocytopenia Syndrome (TTS).

In 2020, amid the Covid-19 outbreak, the United Kingdom (UK) pharmaceutical firm collaborated with the University of Oxford to develop the AZD1222 vaccine. In India, the vaccine produced by AstraZeneca was marketed under the brand name Covishield, manufactured by the Serum Institute of India (SII) in Pune.

What is TTS?

It is a medical condition characterised by the formation of blood clots (thrombosis) alongside a low blood platelets count (thrombocytopenia). Thrombosis occurs when a clot forms within a blood vessel, potentially obstructing blood flow.

Thrombocytopenia denotes a deficiency of platelets in the bloodstream. Platelets play a crucial role in blood clotting, essential for preventing excessive bleeding.

TTS often involves unusual blood clots, notably in the brain (cerebral venous sinus thrombosis) or abdomen. TTS is also known as vaccine-induced immune thrombotic thrombocytopenia (VITT).

What are the symptoms of TTS?

Symptoms of TTS can be severe. Individuals experiencing severe or persistent headaches, blurred vision, chest pain, shortness of breath, leg swelling, or continuous abdominal discomfort should be alert to the possibility of TTS. Additionally, easy bruising or small blood spots beneath the skin, extending beyond the injection site, may indicate the condition.

In 2023, the World Health Organization (WHO) highlighted TTS as a noteworthy adverse event following immunisation with Covid-19 non-replicant adenovirus vector-based vaccines. This includes the AstraZeneca Covid-19 ChAdOx-1 vaccine and the Johnson & Johnson (J&J) Janssen Covid-19 Ad26.COV2-S vaccines.

Watch: Covishield can cause blood clots, low platelet count. Here's all you should know

How did this come to light?

In the UK, AstraZeneca has faced a class action lawsuit over allegations that its vaccine led to fatalities and severe injuries in numerous instances, reported The Telegraph.

During court proceedings, lawyers argued that the Covid-19 vaccine manufactured by AstraZeneca resulted in a side effect that had affected several families.

The first case was registered in 2023 by Jamie Scott, who received the vaccine in April 2021. Shortly after being inoculated with AstraZeneca's vaccine, Scott said that he sustained a permanent brain injury due to the development of a blood clot and brain bleeding, rendering him unable to work.

Kate, Scott’s wife, said, “The medical world has acknowledged for a long time that vaccine-induced immune thrombocytopenia and thrombosis [VITT] was caused by the vaccine.”

However, AstraZeneca informed Scott’s legal representatives in May 2023 that they do not acknowledge TTS as being induced by the vaccine on a general level.

While AstraZeneca is disputing the allegations, it has accepted that its Covid vaccine "can, in very rare cases, cause TTS".

Scott’s wife has demanded an apology and fair compensation for their family and others affected, adding that it took three years for the acknowledgment to materialise.

“We have truth on our side, and we are not going to give up,” she said.

How many cases are filed against AstraZeneca for its Covid vaccine?

According to the latest report, 51 cases have been filed in the High Court by individuals affected by the vaccine and their families, seeking compensation estimated to be as high as UK pound 100 million.

In a legal filing submitted in February, AstraZeneca told the court that its vaccine could, in rare instances, lead to TTS. However, the pharmaceutical company admitted that the precise causal mechanism behind this phenomenon remains unknown.

Legal representatives of people who have sued the company argue that the vaccine is “defective”, and that its efficacy has been “vastly overstated”. AstraZeneca has refute the allegations.