AstraZeneca’s coronavirus vaccine has now been linked to another rare bleeding disorder.
Researchers say about one in 100,000 people given the vaccine will suffer from idiopathic thrombocytopenic purpura (ITP).
The condition can cause mild bruising around the body and can leave some with a purple-dotted rash.
Nearly 350 Brits were affected by a rare separate bleeding disorder after receiving the AstraZeneca vaccine, developed by the University of Oxford.
The complication – blood clots that occur alongside abnormally low platelet levels, block-causing cells – has frightened healthcare leaders into advising under-40s to get a different shot.
ITP can cause mild bruising around the body and can leave some with a purple-dotted rash called petechiae (pictured)
Experts from the University of Edinburgh, who discovered the link with ITP, did not say how many people also developed clots.
But they said it was likely to be a “manifestation” of the main worrying complication.
The researchers spotted the link after analyzing data from 5.4 million people in Scotland between 8 December and 14 April. By that point, 1.7 million had received their first dose of Oxford Jab, while 800,000 had the Pfizer-BioNTech vaccine.
They looked at the medical records of vaccinated individuals to identify any previous problems with ITP, bleeding disorders, or bleeding and compared them to people who had not been vaccinated.
No cases have been linked to Pfizer’s Covid vaccine, which works completely differently.
They said the discovery of that shot – which was administered 24.6 million times in Britain – was “reassuring”.
What is idiopathic thrombocytopenic purpura (ITP)?
ITP is a condition that causes the immune system to destroy platelets.
platelets are blood cells that clot blood and are needed to prevent bleeding and bruising after an injury.
People can get ITP after a virus, vaccine, or certain medications, but the cause is often unknown. It is usually diagnosed with a blood test.
Between 3,000 and 4,000 people in the UK have ITPs.
Someone who doesn’t have enough platelets can bruise very easily or may not be able to stop the bleeding when cut.
Other common symptoms include petechiae – a stinging rash of blood spots that may appear red, purple, or brown – bruises and nosebleeds.
A normal platelet count is between 100 and 400 billion per liter of blood.
Those with ITP are unlikely to suffer from bleeding symptoms unless their platelet count is less than 20 billion per liter of blood.
ITP in children almost always improves without any treatment.
But adults are usually prescribed a short course of steroids to treat the condition.
For the AstraZeneca jab, the risk of developing ITP lasted for nearly four weeks after being hit.
There is no evidence that the AstraZeneca hit caused blood clots despite growing claims, and this remains under investigation.
Experts also insist that the benefits of the vaccine outweigh the risks for the vast majority of adults.
UK health chiefs have only advised under 40s to receive a different vaccine due to their minimal risk of becoming seriously ill, coupled with the very low prevalence of Covid at the time.
The JCVI’s recommendation, which recommends number 10, may change if cases get out of control due to the Indian variant.
The Edinburgh scientists said the risk of ITP after the AstraZeneca vaccine – calculated at 11 per 1 million doses – was similar to the rates observed for the MMR vaccine.
Professor Aziz Sheikh, author of the study, said the “very small risk” of ITP, clotting and bleeding had to be “seen in the context of the very obvious benefits” of jab, which has repeatedly been shown to save lives.
Dr Will Lester, a hematologist consultant at University Hospitals Birmingham NHS Foundation Trust who was not involved in the study, said ITP is often “manageable” and the risk of death from the condition “very rare”.
He insisted that “there is currently no evidence” that any Covid vaccine is riskier than another.
Patients who developed ITP had an average age of 69 and often had at least one underlying health condition, such as heart disease or diabetes.
The first clots that alarmed people who were given the AstraZeneca vaccine were those that appear in the veins near the brains of young adults in a condition called CSVT (sinus vein thrombosis).
Since then, however, people have developed clots in other parts of the body.
All the clots occurred along with thrombocytopenia, an abnormally low number of platelets – an unusual effect because platelets are usually used by the immune system to build clots.
In most cases, people recover completely, and blockages are generally easy to treat if spotted early, but can trigger strokes or heart or lung problems if not noticed.
Symptoms depend entirely on where the clot is located, with brain blocks causing excruciating headaches. Clots in the major arteries of the abdomen can cause persistent stomach pain, and those in the leg can cause swelling of the limbs.
Some countries have decided to stop using the jab altogether, with Denmark and Norway having decided not to implement it. Other nations have restricted it to certain age groups.
The Oxford vaccine was approved in the UK in December and is recommended for use over the age of 40
But the AstraZeneca shot isn’t the only one thought to cause blood clots. Johnson & Johnson’s single-dose vaccine, which has yet to be approved in the UK, has been linked to 28 cases in the US out of over 10.4 million shots.
Researchers in Germany believe the problem lies in the vector adenovirus, a common cold virus used so that both vaccines can enter the body.
Academics investigating the problem say the complication is “completely absent” in mRNA vaccines like Pfizer and Moderna because they have a different delivery mechanism.
Experts from the Goethe University of Frankfurt and the University of Ulm in Helmholtz say that the AstraZeneca vaccine enters the cell’s nucleus, a patch of DNA in the middle. For comparison, Pfizer jab enters the surrounding fluid which acts as a protein factory.
Fragments of coronavirus proteins entering the nucleus can rupture, and the unusual fragments are then expelled into the bloodstream, where they can trigger clotting in a small number of people, the scientists say.
AstraZeneca said in a statement that its Covid vaccine is “highly effective”, helping to save more than 100,000 lives worldwide.
Ensuring vaccine safety is “critical” and the company is working with regulators and the scientific community to understand “extremely rare” blood clots, he said.
The JCVI recommended that children under 39 be given a vaccine other than the Oxford Jab, out of concerns about the very low risk of possible links to blood clots. Data shows that over 40 million people received the first jab in the UK, while over 28 million received the second