LAST UPDATE | 2 Dec 2021

SCIENTISTS BELIEVE THEY may have found the “trigger” behind the extremely rare blood clot complications stemming from the AstraZeneca Covid-19 vaccine.

According to an international team of researchers from Cardiff and the US, the reaction can be traced to the way the adenovirus used by the vaccine to shuttle the coronavirus’ genetic material into cells binds with a specific protein in the blood, known as platelet factor 4 (PF4).

Researchers think this may spark a chain reaction in the immune system which can culminate in the development of blood clots – a condition known as vaccine-induced immune thrombotic thrombocytopenia (VITT).

Professor Alan Parker, from Cardiff University’s School of Medicine, said: “VITT only happens in extremely rare cases because a chain of complex events needs to take place to trigger this ultra-rare side effect.

Our data confirms PF4 can bind to adenoviruses, an important step in unravelling the mechanism underlying VITT. Establishing a mechanism could help to prevent and treat this disorder.

“We hope our findings can be used to better understand the rare side effects of these new vaccines – and potentially to design new and improved vaccines to turn the tide on this global pandemic,” he added.

Scientists from AstraZeneca also took part in the research, which was published in the journal Science Advances.

A spokeswoman for the company told the BBC: “Although the research is not definitive, it offers interesting insights and AstraZeneca is exploring ways to leverage these findings as part of our efforts to remove this extremely rare side effect.”

Covid treatment

UK regulators have approved a drug treatment for Covid-19 which, the makers say, works against the new Omicron variant.

Xevudy (sotrovimab), made by pharmaceutical giant GlaxoSmithKline (GSK), has been found to cut hospital admission and death by 79% in those at risk.

The monoclonal antibody has been authorised by the Medicines and Healthcare products Regulatory Agency for people with mild to moderate Covid-19 who are at high risk of developing severe disease.

GSK and Vir Biotechnology said preclinical data shows the drug “retains activity against key mutations of the new Omicron Sars-CoV-2 variant”.

George Scangos, chief executive of Vir, said: “Sotrovimab was deliberately designed with a mutating virus in mind.

“By targeting a highly conserved region of the spike protein that is less likely to mutate, we hoped to address both the current Sars-CoV-2 virus and future variants that we expected would be inevitable.

“This hypothesis has borne out again and again, with its ongoing ability to maintain activity against all tested variants of concern and interest to date, including key mutations found in Omicron, as demonstrated by preclinical data.

“We have every expectation that this positive trend will continue and are working rapidly to confirm its activity against the full combination sequence of Omicron.”

The body said the drug works by binding to the spike protein on the outside of the Covid-19 virus, which in turn prevents the virus from attaching to and entering human cells, so it cannot replicate in the body.

Based on the clinical trial data, the drug is most effective when taken during the early stages of infection, so the MHRA said it should be given as soon as possible and within five days of symptoms starting.

The drug has been approved for people who have mild to moderate Covid-19 infection and at least one risk factor for developing severe illness.