Should I be worried about the Oxford/AstraZenica Covid vaccine? Your questions answered

That vote of confidence has been backed up by the European medicines watchdog which ruled that unusual blood clots were “very rare side effects” of the jab.

Some other European countries have restricted the vaccine’s use in younger people following reports of cerebral venous sinus thrombosis, a specific type of clot that prevents blood from draining from the brain, as well as low platelet counts – cells that help blood clot. However, Prime Minister Boris Johnson has said people should follow the regulator’s advice and keep getting their jabs.

So what are the risks and should you take it when offered?

l What have the regulators said?

A review by the European Medicines Agency (EMA) safety committee said “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 agency 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, the agency’s 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.”

Nurse prepares to administer AstraZeneca vaccine. Picture: Russell Cheyne/PA Wire

l How many have been affected?

Up to March 31, the MHRA 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 CVST while the other five were thrombosis.

Meanwhile, in Europe, the 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.

Read more: Government reassures public over jab clot fears

l What have others done?

Germany, France, the Netherlands, Sweden and Canada have restricted use of the Oxford vaccine in younger people while Denmark and Norway have paused it.

Nurse prepares to administer AstraZeneca vaccine. Picture Ed Nix

l What has AstraZeneca said?

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”.

On Tuesday, 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.

l 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 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: “These thrombotic events may have been a causal, but rare, adverse event from the Oxford AstraZeneca vaccine. It’s important to emphasise that adverse events happen with all medicines, and vaccines are no exceptions.”

l What other jabs are available?

The UK is using one other vaccines, Pfizer/BioNTech, while a Moderna jab, began its rollout in Wales on Wednesday.

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 trial.

The country has also ordered 30 million doses of a Johnson & Johnson vaccine, which has been shown to be 66 per cent effective in preventing coronavirus infection.

l Are the alternatives safe?

The MHRA has received two reports of blood clots for the Pfizer/BioNTech vaccine out of 11 million first doses and 3.5 million second doses. There is no data on the Moderna vaccine as it is not yet being used widely in the UK.