New Delhi: British drugmaker AstraZeneca admitted covid vaccines could cause blood clots but said these were “extremely rare” after more than 50 such cases were reported in the UK in patients administered jabs that had been made by the Serum Institute of India. 

The company said on Tuesday that patient safety is its highest priority. Regulatory authorities have clear and stringent standards to ensure the safe use of all medicines, including vaccines, it added.

The pharma company said regulators around the world have consistently stated that the benefits of vaccination outweigh the risks of extremely rare potential side-effects.

The company is facing a class action lawsuit in the UK over allegations its vaccine had caused fatalities and severe injuries in numerous instances. Victims involved in up to 51 cases in the UK High Court are seeking damages totalling up to 100 million pounds.

The vaccine, known by various brand names, including Covishield in India, was developed in the UK and manufactured by SII in India. These vaccines were sold around the world. 

Following the lawsuit, AstraZeneca has expressed sympathy for those affected by adverse reactions to its vaccine.

AstraZeneca on Monday admitted in a legal filing in the UK that its vaccine can result in a condition known as thrombosis with thrombocytopenia syndrome (TTS) in rare instances. 

TTS involves the formation of blood clots accompanied by a low platelet count, which is crucial for blood clotting.

“It is admitted that the AZ vaccine can, in very rare cases, cause TTS. The causal mechanism is not known. Further, TTS can also occur in the absence of the AZ vaccine (or any vaccine). Causation in any individual case will be a matter for expert evidence,” the drugmaker said.

Highest priority

“Our sympathy goes out to anyone who has lost loved ones or reported health problems. Patient safety is our highest priority and regulatory authorities have clear and stringent standards to ensure the safe use of all medicines, including vaccines, ” it said in a statement on Tuesday.

The company said that from the body of evidence in clinical trials and real-world data, the AstraZeneca-Oxford vaccine has continuously been shown to have an acceptable safety profile.

Covishield, a vaccine developed by AstraZeneca and Oxford University, was extensively administered to the Indian population.

Recombinant tech

It is a recombinant, replication-deficient chimpanzee adenovirus vector encoding the SARS-CoV-2 Spike (S) glycoprotein. Following administration, the genetic material of part of coronavirus is expressed which stimulates an immune response.

Queries sent to the Serum Institute of India and India’s health ministry remained unanswered.

In 2022, a reputed medical journal Pubmed published a report citing a short-term adverse event following two doses of Covishield, but these were mild and short lived. 

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Published: 30 Apr 2024, 07:07 PM IST