Medical expert Dr Rajeev Jayadevan said that Thrombosis Thrombocytopenia Syndrome (TTS) refers to the clot in blood vessels, and it occurs in very rare cases, following the use of certain types of vaccines.

Acknowledging that the Covid vaccines have helped in preventing numerous deaths, Jayadevan, who is the Co-Chairman of National Indian Medical Association (IMA) Covid Task Force in Kerala, stated that reports of such cases have also been highlighted in many reports.

"TTS is thrombosis with thrombocytopenia syndrome, which is basically clot in blood vessels of the brain or elsewhere, along with a low platelet count. It is known to occur in very rare instances following certain types of vaccines and also from other causes. According to the WHO, adenovirus vector vaccines in particular have been rarely associated with this condition," he told ANI."

Although Covid vaccines have prevented numerous deaths, reports of these extremely rare but potentially serious immune mediated events have also been published in reputed journals," Dr Jayadevan added.

This comes in the wake of a recent admission by AstraZeneca, the pharmaceutical company, that its Covid vaccine Covishield and Vaxzevria "can, in very rare cases, cause TTS."

According to several UK media reports, AstraZeneca has made the admission in court documents in connection with a case that alleges that the vaccine, developed with the University of Oxford, caused death and serious injury in dozens of cases.

The Serum Institute of India produced Covid-19 vaccine named Covishield but not using mRNA platform. It has been prepared using the viral vector platform. In the vaccine, a chimpanzee adenovirus - ChAdOx1 - has been modified to enable it to carry the Covid-19 spike protein into the cells of humans. This cold virus is basically incapable of infecting the receiver, but can very well teach the immune system to prepare a mechanism against such viruses.

The same technology was used to prepare vaccines for viruses like Ebola.

Amid reports about clot in blood vessels in the UK media, the Serum Institute of India did not respond to the query.

Notably in 2023, the World Health Organisation (WHO) said in its report that TTS emerged as a new adverse event following immunisation in individuals vaccinated with Covid-19 non-replicant adenovirus vector-based vaccines.

This refers to the AstraZeneca Covid-19 ChAdOx-1 vaccine and the Johnson & Johnson (J&J) Janssen Covid-19 Ad26.COV2-S vaccines. "TTS is a serious and life-threatening adverse event. WHO has issued this interim emergency guidance to increase awareness about TTS in the context of Covid-19 vaccination and help healthcare providers in the assessment and management of potential TTS cases," the 2023 statement by WHO read.

However, Union Health Minister Mansukh Mandaviya in March 2024 at 'ANI Dialogues - Navigating India's health sector' said that ICMR has done a detailed study which shows that Covid-19 vaccine is not responsible for heart attacks, and an individual's lifestyle and factors such as binge drinking could be among underlying causes.

Mandaviya said, "If someone has a stroke today, they think it is because of the Covid vaccine. ICMR has done a detailed study that the (Covid) vaccine is not responsible for heart attacks."

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