A preservative in AstraZeneca’s Covid vaccine can trigger a rare overreaction of the immune system that causes blood clots, a scientist said.
A small number of people who have received the jab or the one done by Johnson & Johnson have developed a bleeding disease which has frightened some countries by turning their backs on them.
The reasons for this are unclear, but a German expert has suggested it could start with a chemical used to make the vaccine.
EDTA, or ethylenediaminetetraacetic acid, can trigger an overreaction by forming clumps with platelets in the bloodstream.
EDTA – commonly used in drugs and cosmetics – can leak more of the ingredients from the jab intramuscularly into the blood vessels.
Dr Andreas Greinacher said they could cause the body to overproduce antibodies and trigger a second reaction from the immune system which then begins to clot the blood.
Medical regulators in the UK have spotted 262 cases of blood clots in 23.36 million people who received AstraZeneca jab – a rate of around one in 100,000.
Clots remain rare and pose a much lower risk than Covid, but people under the age of 40 have been advised to get vaccinated if they can, out of caution.
The AstraZeneca Covid vaccine remains one of the most widely used in the world because it prevents severe Covid and is widely available, but some countries have limited its use only to the elderly who are at a higher risk of the outweighing coronavirus. the risk of side effects (photo: A nurse in Dublin fills a syringe with vaccine)
WHAT IS THE THEORY?
Dr. Greinacher’s theory is based on events that can be triggered by the preservative EDTA in the AstraZeneca vaccine, Pharmaceutical Technology reports:
- EDTA increases the amount of vaccine proteins that escape from muscle into the blood;
- The proteins in the vaccine interact with the naturally circulating platelets to form clumps, activating the platelets;
- Platelet activation releases another protein (platelet factor 4 or PL4) which adheres to vaccine proteins, including virus fragments;
- The presence of PL4 and proteins in the blood triggers the release of antibodies from the immune system;
- A large number of anti-PL4 antibodies trigger a stronger immune response, some of which may be inflammation (swelling) and increased blood clotting in some people.
MHRA Director Dr June Raine said last week that the benefits of AstraZeneca continue to outweigh the risks for the “vast majority of people”.
But she said: “The balance between benefits and risks is very favorable for older people but is more finely balanced for younger people.
“We recommend that you take this shift in evidence into account when considering vaccine use.
The government opted for a policy of giving adults 40 years of age or younger a choice of vaccines when they go to their appointments, as low platelet clots seemed to be more common among them, at around one in 60,000 people.
The NHS deployment has expanded to 38 and 39 years old today for the first time.
One of the main theories as to why clots happen was that the body overproduced antibodies that triggered a reaction that led to blood clotting.
Now Dr Andreas Greinacher, a blood expert and immunologist at the University of Greifswald, may be able to explain why, Pharmaceutical Technology reports.
Dr Greinacher and his colleagues have conducted studies in mice that suggest that EDTA causes proteins from the vaccine fluid to leak into the bloodstream and activate platelets by hitting them.
Platelets are tiny components of clots and always circulate in the blood in case they are needed to heal an injury.
But once they’re triggered, they set off a chain reaction of immune responses, releasing another protein, known as PL4, which sticks to more proteins in the vaccine and starts forming more lumps.
Doctors say they found cure for vaccinated blood clots
Doctors say they may have discovered a life-saving cure for the type of blood clots linked to Covid vaccines.
Doctors in Aurora, Colorado tried a blood thinner known as bivalirudin when a 40-year-old woman developed a blood clot in her brain two weeks after receiving the J&J vaccine.
Not only did the medicine help break the woman’s blood clots, she was able to leave the hospital and go home six days later.
Days earlier, the Centers for Disease Control and Prevention had advised doctors not to use heparin, a blood thinner.
This is because the condition – blood clots alongside low platelet levels – is very similar to what can be caused by heparin, called heparin-induced thrombocytopenia.
The new condition is called vaccine-induced thrombocytopenia.
Medical chiefs have yet to announce a standard treatment for those diagnosed, although the usual treatments for blood clots are likely to be used.
These lumps then alarm the immune system and antibodies – not Covid’s – are produced to destroy the clumps of proteins, antibodies and platelets.
Large amounts of these antibodies then trigger a higher level reaction of the immune system which can include swelling of blood vessels and blood clots, potentially leading to the clotting seen in vaccinated patients.
The highest profile of cases involved a vein exiting the brain, a condition known as CVST, but the majority of cases in the UK (163 of 262) were found elsewhere in the body.
A total of 51 people have died in the UK after developing a blood clot after the vaccination.
Some countries, including Denmark and Norway, have completely stopped using the AstraZeneca vaccine while others have restricted it to the elderly.
Health officials in the UK last week said people under 40 should be offered an alternative to the shot because the risks and benefits were finely balanced.
For older people who are at real risk of dying if they catch Covid, the benefits of protecting against the virus clearly outweigh the negative side effects.
Experts have said the infection rate in the UK is now so low that the risk of rare clots outweighs that of Covid in young adults, who often only suffer from mild illness.
They will be offered Pfizer or Moderna vaccines instead, as long as there is sufficient supply and this does not delay deployment.
Anyone, regardless of age, who received their first dose of AstraZeneca vaccine and who has not suffered from the complication is invited to come for the second.
England’s deputy chief medical officer Professor Jonathan Van-Tam has said the change will not affect the government’s goal of vaccinating all adults by July 31.
“Our vaccine supply schedule will support change without limiting the speed and scale of vaccine deployment,” he told a televised press conference in Downing Street.
“I expect that we are still on track to deliver a first dose to all adults by the end of July.
On April 7, it was previously recommended to offer healthy under 30s an alternative to AstraZeneca.