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Crafted from the modified chimpanzee adenovirus ChAdOx1, the Oxford-AstraZeneca COVID vaccine, known as Covishield in India and Vaxzevria in Europe, harnesses viral vector technology to safeguard against the pandemic.

The Oxford-AstraZeneca COVID Vaccine

New Delhi: Doctors cautioned today that Thrombosis Thrombocytopenia Syndrome (TTS), a rare blood clot disorder, is a concerning side effect of the AstraZeneca Covid vaccine, with risks outweighing benefits. This follows reports confirming AstraZeneca's acknowledgment, for the first time in court documents, of the vaccine's potential to elevate the risk of this uncommon but severe condition.

The Oxford-AstraZeneca Covid vaccine, marketed as Covishield in India and Vaxzevria in Europe, employs viral vector technology utilizing the modified chimpanzee adenovirus ChAdOx1.

Covishield, produced and distributed in India through a partnership with the Serum Institute of India (SII), saw extensive usage, reaching nearly 90 percent of the Indian populace.

Infectious disease expert Dr. Ishwar Gilada explained, "Thrombotic Thrombocytopenic Syndrome (TTS) is a rare yet very serious adverse effect, occurring as part of Vaccine-induced Immune Thrombotic Thrombocytopenic Purpura (VITTP). While the incidence remains low, at approximately one in 50,000 (0.002 percent), in large populations, the numbers become significant."

Dr. Rajeev Jayadevan, co-chairman of the Indian Medical Association's National Covid-19 Task Force, stated, "TTS is a rare condition stemming from an abnormal immune response. Although multifactorial, it has been associated with adenovirus vector vaccines, as highlighted in a report by the WHO dated May 27, 2021."

AstraZeneca's acknowledgment in UK court documents marks the first instance where the pharmaceutical company has conceded to the vaccine's potential to pose a risk of rare blood clots, as reported by The Telegraph.

In the UK High Court, about 51 cases have been filed against the pharmaceutical giant, alleging that its Covid vaccine led to fatalities and serious injuries, seeking damages estimated up to 100 million pounds.

While AstraZeneca contests these claims, it conceded, in a legal filing submitted to the High Court in February, that its Covid vaccine "can, in very rare cases, cause TTS," The Telegraph reported.

TTS manifests as blood clots and a reduced blood platelet count.

In India, nearly 90 percent of vaccine recipients received the AstraZeneca vaccine, known as Covishield. This vaccine, developed from a modified chimpanzee adenovirus, targets the SARS-CoV-2 spike protein genetic sequence, said Dr. Ishwar, Secretary General of the People's Health Organisation-India, Mumbai.

Explaining the potential mechanism of TTS, Dr. Ishwar mentioned that while the vaccine is primarily administered into the arm muscle, in some cases, it may enter the bloodstream. Once in the bloodstream, the adenovirus in the vaccine can bind to a blood protein called platelet factor 4 (PF4). Though PF4 typically aids in blood coagulation, in rare instances, the body's immune system may mistake it for a foreign entity, triggering antibody release and leading to clot formation.

Regarding concerns among Covishield recipients, Dr. Ishwar reassured, "No, the occurrence is extremely rare."

Dr. Rajeev emphasized, "Vaccinated individuals face a lower overall risk of Covid-related mortality and post-Covid complications such as heart attacks and strokes."

Despite exceedingly rare adverse effects, the benefits of Covid vaccines far outweigh the risks, preventing countless deaths. In the US, for instance, Covid vaccines have averted hundreds of thousands of fatalities, underscoring the importance of vaccination.