GUWAHATI: Global pharmaceutical giant AstraZeneca has admitted that its COVID-19 vaccine, Covishield, manufactured under license in India by Serum Institute of India (SII), could cause Thrombosis with Thrombocytopenia Syndrome (TTS), a condition characterised by blood clots and low platelet counts. The admission came during court proceedings related to legal claims in the United Kingdom alleging that the vaccine caused health complications and fatalities.
TTS is a rare condition that occurs when blood clots form in blood vessels, potentially leading to serious health risks such as strokes, heart attacks, and other complications. Symptoms of TTS can include breathlessness, chest or limb pain, pinhead-sized red spots, or bruising of the skin.
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AstraZeneca’s court admission follows lawsuits filed by individuals and families claiming damages due to adverse reactions from the vaccine. According to UK media reports, one case was lodged by a man who suffered a brain injury after developing a blood clot following his vaccination in April 2021. In total, fifty-one cases have been lodged in the UK High Court, with damages claims estimated to be worth up to £100 million.
While the Indian government had issued a fact sheet in January 2021 advising caution for those with thrombocytopenia, other countries temporarily paused the use of AstraZeneca's vaccine in March 2021 after reports of blood clotting. By April 2021, the World Health Organization (WHO) acknowledged TTS as a rare event following Covishield vaccinations.
Despite these reports, India's Union Health Ministry noted that the overall risk remains "minuscule" and that Covishield "continues to have a definite positive benefit-risk profile." The Ministry reported that 26 potential thromboembolic events, or formation of clots in blood vessels, had been reported since Covishield's rollout in January 2021, equating to 0.61 cases per million doses. It also indicated that the risk of TTS in South and Southeast Asian descent is 70% less than in those of European descent.
Recent data from India's committee on Adverse Events Following Immunisation (AEFI) shows that 36 cases of TTS were confirmed to be caused by Covishield, with 18 resulting in death. Most of these cases were reported in 2021, the first year of Covid-19 vaccinations in India. No cases of thromboembolic events were reported with Covaxin, Bharat Biotech's indigenous vaccine.
