Scientists find 'trigger' for rare blood clots linked to AstraZeneca jab
It's traced back to how one of the vaccine's components binds with a protein in the blood
Last updated 2nd Dec 2021
Scientists believe they've found the "trigger" that leads to extremely rare blood clots after the Oxford-AstraZeneca Covid vaccine.
According to an international team of scientists from Cardiff and the US, the reaction can be traced to the way one of the vaccine components binds with a specific protein in the blood.
Specifically, when the adenovirus, used by the vaccine to shuttle the coronavirus' genetic material into cells, binds with 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.
The condition is 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."
Learn more about the coronavirus vaccines:
What is the Pfizer-BioNTech vaccine?
The Pfizer-BioNTech vaccine was approved for use in the UK on 2 December 2020. Britain was the first country in the world to approve the jab, which offers up to 95% protection against Covid-19. Pfizer is an American pharmaceutical firm while BioNTech is a German biotechnology company. The vaccine is very delicate and has to be stored at -70 degrees, limiting the number of sites that can administer the jab.
What is the Oxford/AstraZeneca vaccine?
A vaccine developed by Oxford University and pharmaceutical company AstraZeneca became the second vaccine approved for UK use on 30 December 2020. This vaccine was considered "the way out" of the pandemic in the UK, thanks to the fact it is easier to store than the Pfizer jab, making it well equipped for mass roll out. GPs and vaccination centres across the country began administering the jab in early January 2021. Under 30's in the U.K. were given the option to choose a different vaccine to this due to small risks of very rare blood clots. Instead, under-30s would typically choose the Pfizer jab or later, the moderna jab.
What is the Moderna vaccine?
The third vaccine approved for UK use on 8 January 2021 was developed by American firm Moderna. 24-year-old Elle Taylor from Wales became the first person in the UK to receive the Moderna jab in April. The Moderna vaccine is similar to the Pfizer jab in how it works but is even easier to roll out as it can be stored at -20 degrees rather than -70.
What is the Johnson & Johnson vaccine
The fourth vaccine to be be approved in the UK was Johnson & Johnson's vaccine, released under the name Janssen. Notably, It is also the first single shot vaccine in use during this vaccine rollout.
Who was the first person to receive the Pfizer vaccine?
90-year-old Margaret Keenan became the first patient in the world to be vaccinated against Covid-19 outside a clinical trial. She received her jab on 8 December 2020 at Coventry's University Hospital. Mrs Keenan, who lives in Coventry, became somewhat of a fashion influencer after the charity t-shirt she wore to her vaccination appointment sold out. Profits went towards buying Christmas presents for hospital patients. The grandmother advised everyone who was offered the vaccine to take it, saying "If I can have it at 90, then you can have it too."
Who was the first person to receive the Oxford vaccine?
Meanwhile, Brian Pinker from Oxford was first to receive the AstraZeneca jab outside of a clinical trial at the age of 82. Mr Pinker, who was vaccinated on 4 January 2021, praised the medical teams administering the vaccine, saying it would allow him to "really look forward" to celebrating his 48th wedding anniversary with wife Shirley later on in the year.
When will I receive the vaccine?
Vaccines were offered according to vulnerability levels. First to be offered the jab were people in care homes and their carers, followed by those over 80 and health and social care workers. People aged 65 and above were next on the priority list and then high-risk adults under the age of 65 followed by moderate risk adults under 65. The vaccine was then rolled out by age group.
How will I know when it's my turn to get vaccinated?
When it is your turn to receive the vaccination, you will be informed by the NHS. You should only attend vaccination sites if you have been told to do so. Vaccines are provided for free by the NHS and they will never ask for bank details. Find out more about vaccine scams here.
What is a vaccine passport?
The Government debate the idea of a vaccine passport as proof of full vaccination required to enter venues like nightclubs. Health Secretary Sajid Javid later "ditched" the idea and ensured clubbers that they no longer need to be double jabbed by the end of September 2021 to get into Nightclubs or big events.
Do I need a booster jab?
Pfizer/BioNTech booster jabs are rolled out as part of the Government's winter covid plan. Shots can be given to people aged 50 and over, those in care homes and frontline health and social care workers. All those who are clinically extremely vulnerable and anyone aged 16 to 65 in an at-risk group for Covid will also be eligible for a jab. There must be at least 6 months between a 2nd vaccine dose and a booster jab.
Oxford jab scientist Sarah Gilbert says booster jabs are "not needed for all" and that they should instead go to countries with low vaccination rates.
Will children be vaccinated?
The government have also made vaccines available to children aged between 12-15 as part of the country's winter Covid plan.
What about five to 11-year-olds getting vaccinated?
All 5 to 11-year-olds in England can now receive a coronavirus jab, following advice from the JCVI and the same decision being made in Scotland and Wales. Northern Ireland is also expanding their vaccination programme to include the 5-11 age range. It means almost six million children in the UK will be offered the Covid-19 vaccination.