Meanwhile, in a separate update on its investigations on Wednesday, the European medicines watchdog has ruled that unusual blood clots were “very rare side effects” of the jab. Scientists have also insisted that further research is needed to understand more about the risk of these rare blood clots.
Some European countries have restricted the vaccine for younger people following reports of cerebral venous sinus thrombosis (CVST), a specific type of clot that prevents blood from draining from the brain, as well as low platelet counts – cells that help blood clot.
Prime Minister Boris Johnson has said people should follow the regulator’s advice and keep getting their jabs.
Read on to find out the latest about the Oxford/AstraZeneca vaccine, and to have your questions answered by our expert, The Telegraph’s Global Health Security Editor Paul Nuki, below.
What do we know about any link between the AstraZeneca vaccine and blood clots?
Up to March 31, the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) has received 79 reports of blood clots accompanied by low blood platelet count, all in people who had their first dose of the vaccine.
Of these 79, a total of 19 people have died, although it has not been established what the cause was in every case.
The 79 cases occurred in 51 women and 28 men, aged from 18 to 79.
Of the 19 who died, three were under the age of 30, the MHRA said. Some 14 of those cases were Cerebral venous sinus thrombosis (CVST) while the other five were thrombosis.
Meanwhile, in Europe, the European Medicines Agency (EMA) has carried out an in-depth review of 62 cases of CVST and 24 cases of splanchnic vein thrombosis in which 18 people died.
What have the regulators said?
A review by EMA safety committee concluded on Wednesday that “unusual blood clots with low blood platelets should be listed as very rare side effects” of the AstraZeneca vaccine.
Emer Cooke, executive director of the EMA, said: “These are very rare side effects.
“The risk of mortality from Covid is much greater than risk of mortality from these side effects.”
The MHRA said there were still huge benefits of the vaccine in preventing Covid-19 and serious disease but added that due to a very small number of blood clots in younger people, those under the age of 30 will be offered Pfizer or Moderna jabs instead.
Dr June Raine, MHRA chief executive, added: “Anyone who has symptoms four days after vaccination or more should seek prompt medical advice – a new onset of a severe or persistent headache or blurred vision, shortness of breath, chest pain, leg swelling, persistent abdominal pain or indeed unusual skin bruising or pin-point spots beyond the injection site.”
How have other countries reacted?
Germany, France, the Netherlands, Sweden and Canada have restricted the use of the AstraZeneca vaccine in younger people while Denmark and Norway have paused administering it. Italy and Spain have stopped the use of the jab in the under-60s.
What has AstraZeneca said?
Last month, AstraZeneca said it was analysing its database to understand “whether these very rare cases of blood clots associated with thrombocytopenia (low blood platelet count) occur any more commonly than would be expected naturally in a population of millions of people”.
Meanwhile on Tuesday, April 6, a trial of the Oxford/AstraZeneca vaccine on children was paused, but the scientists involved said there were no safety concerns with the trial itself and they were waiting for further information from the MHRA.
What are the experts saying?
Scientists in the UK have said urgent research is needed to understand more about the risk of these rare blood clots.
David Werring, professor of clinical neurology at the UCL Institute of Neurology, said: “The EMA and MHRA statements are helpful in providing further clarity about the very rare blood clots with low blood platelet counts – mainly in the brain (cerebral venous sinus thrombosis) but also in other parts of the body – that have occurred after the AstraZeneca vaccine.
“Both the EMA and MHRA emphasise that the overall benefit of the vaccine in preventing illness, hospitalisation and death from Covid-19 clearly outweighs the risks of this rare potential complication; thus, vaccination programmes should continue as planned.
“We still urgently need more research to first understand which individuals are at highest risk of these unusual blood clots in the brain, which although very rare, can often be serious or fatal.”
Dr Michael Head, senior research fellow in Global Health, University of Southampton, said that while the link is not proven, it is now thought to be increasingly plausible.
He said: “We have seen an update from the UK and EU regulators, suggesting that these thrombotic events may have been a causal, but rare, adverse event from the Oxford AstraZeneca vaccine.”
He added: “It’s important to emphasise that adverse events happen with all medicines, and vaccines are no exceptions.
“Safety surveillance is vital in picking up and assessing signals that emerge from the data.”
What are the side effects of the Oxford/AstraZeneca vaccine?
The AstraZeneca vaccine lists the following side-effects that can occur after the jab: tenderness, pain, warmth, itching or bruising where the injection is given, generally feeling unwell, feeling tired, chills or feeling feverish, headache, feeling sick (nausea), joint pain or muscle ache.
Ian Douglas, professor of pharmacoepidemiology at London School of Hygiene and Tropical Medicine, explains that these side-effects are “pretty common” and occur in more than one in 10 people who are given the vaccine.
When should I see a doctor?
While some people will experience side-effects from the jab, experts have said that certain symptoms may be a sign of a more serious condition which needs immediate medical attention.
Prof Beverley Hunt, medical director at the charity Thrombosis UK, said thrombosis in the head can present as an extremely bad headache.
“We’ve seen patients who have been presenting with thrombosis in the head or abdomen from about day four after the vaccine,” she said.
“I think it’s very important to tell people that lots of people get side effects from the AstraZeneca vaccine and they usually settle down by day four or five.
“What we’ve seen is people presenting with the worst headache they have ever had on day four and they have proved to have thrombosis in the large vein of the head.”
What factors increase the risk of blood clots?
Blood clots are rare in young, healthy people. You’re more likely to get them if you:
Are staying in or recently left hospital – especially if you cannot move around much (like after an operation)
Are using combined hormonal contraception such as the combined pill, contraceptive patch or vaginal ring
Have had a blood clot before
Are pregnant or have just had a baby
Have an inflammatory condition such as Crohn’s disease or rheumatoid arthritis
Meanwhile, preliminary results announced on Tuesday from the trials of the Valneva Covid-19 vaccine, which is set to be manufactured in the UK, have shown it produces a “strong immune response”, paving the way for a phase three clinical trial.
The UK has an in-principle agreement for 60 million doses of the Valneva jab, with an option to acquire a further 130 million doses from 2022-2025.
The country has also ordered 30 million doses of a coronavirus vaccine developed by Johnson & Johnson, which has been shown to be 66 per cent effective in preventing coronavirus infection.
Both the Valneva and Johnson & Johnson jabs will need regulatory approval for use in the UK, once data from later-stage trials become available.
We asked Telegraph readers for their questions on the vaccines that have been rolled out in the UK. Our expert, The Telegraph’s Global Health Security Editor Paul Nuki, answered readers’ questions on Thursday April 8.
Read on for a selection of the best questions from the Q&A.
What are the blood clot risks of the different vaccines currently used in the UK?
Q: What are the blood clot risks of the used vaccines apart from the AstraZeneca vaccine? How do they compare?
A: The other vaccines have not been associated with a raised incidence of clotting. With AZ there does seem to be a raised risk but the problem remains extremely rare.
The MHRA has said up to March 31, it had received “two reports of blood clots (thromboembolism) reported with thrombocytopenia for the Pfizer/BioNTech vaccine”.
By this date, approximately 11 million first doses and 3.5 million second doses of the vaccine had been given, the MHRA said.
There is no data on the Moderna vaccine as it is not yet being used widely in the UK.
I’ve had one dose of AstraZeneca, but I’m under 30, what vaccine will I get for my second dose?
Q: If the AstraZeneca vaccine is banned in an age group what happens for my second dose if l had AstraZeneca for my first?
A: The AZ vaccine is not being banned in any age group. It is just that those under 30 are being offered a choice if an alternative is available. If you have had one dose of the AZ jab the very clear advice is that you should have your second. Any risk is tiny and the upside enormous, especially if we get another surge in infections later in the year –which is likely.
Is there evidence to suggest that we should have different vaccines for different doses?
Q: What evidence is available showing one jab of AstraZeneca vaccine and one jab of Pfizer vaccine provides better efficacy? Is it possible to get this treatment here in England?
A: I’m not aware of there being any evidence yet that mixing jabs has any additional benefit and there may be risks. It’s possible but we will only find out once proper trials have been done. If you search online you may be able to enter one.
Why should I risk getting a vaccine if I have already had Covid?
Q: Having had Covid (no symptoms, but loss of smell and taste), I fail to see why people not at risk, such as myself, are required to take the additional risk of vaccination. Why not stop after all the vulnerable are vaccinated?
A: The natural immunity you got when you first had Covid may not last long, leaving you exposed in future. Even in the short term, the immunity you have may not protect you against some of the new variants. There are now plenty of examples of people who have caught the virus twice, some seriously. Also, the risk of having the vaccine is tiny – about one in 100,000 according to the bigger dataset from the EU. Many things you do day in day out have a higher risk than that – driving, for example.
Could the AstraZeneca vaccine have caused my husband’s blood clot?
Q:My 85-year-old husband died from a blood clot on the brain and the hospital said he had a stroke but he didn’t have any symptoms of a stroke. He had his first vaccination three months ago and was due to get his second this Friday. Could the AstraZeneca vaccine have caused the blood clot?
Paul: If the clot occurred three months after his inoculation it seems unlikely there is any connection but you might talk to your GP to get their view if you have not already. It’s important to remember that clots and strokes become much more common with age and, at 85, are far from unusual.
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