Astrazeneca Covid vaccine Q&A: What we know about blood clots, side effects and risks for under-30s

The risk of a rare brain clot from coronavirus is approximately eight times greater than the risk presented by the AstraZeneca jab, an Oxford University study has found.

This research - which is yet to be peer-reviewed - comes after the UK medicines regulator decision to suspend AstraZeneca rollout among the under-30s, despite evidence that the benefits of the vaccine continue to outweigh any risks.

Meanwhile, in a separate update on its investigations on Apr 7, the European medicines watchdog 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.

On Apr 8, Health Secretary Matt Hancock reiterated that the vaccines currently in use in the UK, including the newly available Moderna vaccine, remained "safe".

The Moderna coronavirus vaccine is the third jab to be rolled out in the UK, and was first administered to people in Wales on Apr 7, with the jab being administered at 20 sites across England from Apr 13.

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.

It comes as researchers at Icahn School of Medicine at Mount Sinai, New York said on Apr 16 that previous coronavirus infection does not fully protect young people against reinfection.

Professor Stuart Sealfon, author of the study, said that despite previous infection and the presence of antibodies, vaccination is still necessary to boost immune responses, prevent reinfection and reduce transmission. Researchers added that young people should take up the vaccine whenever possible.

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 Mar 31, the UK's Medicines and Healthcare products Regulatory Agency (MHRA) had 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 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 Apr 7 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: "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, the Netherlands, Sweden and Canada have restricted the use of the AstraZeneca vaccine in younger people. Italy and Spain have stopped the use of the jab in the under-60s.

It comes as Denmark announced on Apr 14 it would stop administering Oxford/AstraZeneca's Covid-19 vaccine following its possible link to very rare cases of blood clots, several Danish media outlets reported, citing unnamed sources.

The decision, which would remove the shot from Denmark's vaccination scheme, could delay the country's vaccine rollout by up to four weeks, based on previous statements by health bodies.

France has said under 55s who have had a first AstraZeneca dose should take a different vaccine for the second. Olivier Véran, the country's health minister, said the new advice will be that the Moderna and Pfizer vaccines should be used for their second dose.

While Spain will study the effects of mixing different coronavirus vaccines, government researchers said on Apr 19, responding to shifting guidelines on the safety of the AstraZeneca's shot.

Also, Australia has doubled its order of the Pfizer Covid-19 vaccine, as the country races to overhaul its inoculation plan over concerns about the risks of blood clots with the AstraZeneca vaccine.

What has AstraZeneca said?

In March of this year, 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 Apr 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.

In response to these concerns, an Oxford University study examined the incidence of blood clotting on the brain in coronavirus patients and AstraZeneca recipients, finding that the occurrence of brain clots from coronavirus was eight times greater the risk presented by the AstraZeneca jab.

Sir John Bell, Oxford University's Professor of Medicine, has stated that he expects all vaccines to have "some background level of clotting issues". Bell went on to say that the data on this issue was still being collected for further study.

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 about the Johnson and Johnson vaccine and blood clots?

Regulators in the United States have paused the roll out of the Johnson and Johnson vaccine after six people suffered blood clots two weeks after receiving the jab - one person died. Dr Anthony Fauci, who leads the US response, said the pause would probably last just days while experts review the vaccine's safety. Regulators say the decision is based on an "abundance of caution".

The decision is already being felt more widely: the company has delayed shipments of the vaccine to Europe. And South Africa, which decided to stop using the AstraZeneca vaccine because of lack of efficacy against a new variant, has also put its campaign on pause.

On April 20 the European Medicines Agency (EMA) said there was a possible link between Johnson & Johnson's Covid-19 vaccine and rare blood clots but said the benefits of the J&J vaccine far outweighed the risks and that further investigations would continue.

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 overweight

• Smoke

• 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

What other vaccines are available?

The UK is currently using two vaccines, Pfizer/BioNTech and Oxford/AstraZeneca, while a third coronavirus vaccine, the Moderna jab, began its rollout in Wales on Apr 7.

Meanwhile, preliminary results announced on Apr 6 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.

The deputy chairman of the Joint Committee on Vaccination and Immunisation, Prof Anthony Harnden, has said that mixing vaccines could improve protection against coronavirus.

Prof Harnden went on to state that different vaccine types could coalesce to boost the immune system and provide a longer-lasting response. He also said a "mix and match" approach could make future rollouts more flexible.

Readers' questions

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 them 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.

Do you have a question about the AstraZeneca vaccine or any of the other vaccines currently in use in the UK? Leave your question below