A nationwide study by the Indian Council of Medical Research-National Institute of Epidemiology (ICMR-NIE), conducted across 25 tertiary hospitals, has found no link between Covid-19 vaccination and an increased risk of thrombotic events, including heart attacks, among young adults aged 18-45 in India.A thrombotic event refers to the formation of a blood clot inside a blood vessel, obstructing the normal flow of blood. The study, titled “Factors Associated with Thrombotic Events Among Young Adults in India, 2021-23: A Multi-centric Hospital-Based Matched Case-Control Study”, found that thrombosis was largely driven by established medical and lifestyle risk factors, including smoking, pre-existing comorbidities, a family history of clotting disorders and prior severe Covid-19 infection.By May 2023, 97 per cent of eligible individuals in India had received at least one dose of a Covid-19 vaccine, while 90 per cent had received the first two doses. The precautionary third dose was initially administered to healthcare and frontline workers, as well as people aged over 60 years with comorbidities, in January 2022. It was subsequently extended to all individuals aged above 60 years and, from April 2022, to all adults aged 18 years and above.Highlighting the protective benefits of vaccination, the study noted that extensive evidence from India and abroad has established that Covid-19 vaccines significantly reduce the risk of severe disease, hospitalisation, death and long-term complications.The researchers analysed 432 cases of acute myocardial infarction and 767 cases of thrombotic events. “Acute myocardial infarction was associated with a prior history of thrombotic events. Receiving two or more doses of any Covid-19 vaccine was not associated with acute myocardial infarction. Analyses showed an association between thrombotic events and a prior history of thrombosis, comorbidities, smoking, prior Covid-19 hospitalisation and family history of thrombotic events. There was no association between thrombotic events and receipt of two or more vaccine doses,” the study said.The study, co-authored by Dr Manoj Murhekar, Director of ICMR-NIE, concluded that Covid-19 vaccination did not increase the risk of thrombotic events, particularly acute myocardial infarction, among young adults during a period of widespread SARS-CoV-2 transmission.