AstraZeneca vaccine: does Oxford Covid vaccine cause blood clots, what are the side effects and is it safe?

The UK government have continued to roll out the Oxford/AstraZeneca vaccine, as no correlation between the vaccine an blood clots have been found so far (Picture: Getty Images)

More than 17 million people in the UK and across Europe have now received the Oxford-AstraZeneca vaccine, but many European countries have suspended usage after reports of blood clotting.

Norway and Denmark reported that there had been significant adverse effects from patients who had received the UK-produced vaccine, but AstraZeneca have disputed claims that the vaccine carries health risks.

On 15 March, France, Spain and Germany confirmed they would also temporarily halt the roll-out of the AstraZeneca vaccine as a ‘precaution’ over concerns the vaccine is linked to blood clots.

However, a new study carried out in the US has found no safety concerns linked to the vaccine.

So, is the Oxford AstraZeneca vaccine safe and what are the most common side effects? This is what you need to know.

Is the Oxford AstraZeneca vaccine safe?

There is an ongoing European investigation into reports that a small number of people have died from blood clots, after receiving the Oxford AstraZeneca vaccine.

AstraZeneca - the company producing the vaccine - have stated there has been no proven increased risk of deep vein thrombosis or pulmonary embolism as result of its vaccine.

A spokesperson for AstraZeneca said the drug's safety had been studied extensively in clinical trials and "Regulators have clear and stringent efficacy and safety standards for the approval of any new medicine.”

On 22 March, a US study was also published which involved 32,449 participants in the US, Chile and Peru – 20,000 of whom were given the vaccine, with the rest were given dummy jabs.

The study found the vaccine was 79 per cent effective at preventing symptomatic Covid-19 and 100 per cent effective at preventing severe illness and hospitalisation. It was also effective in all ages, including the over-65s.

An independent data safety monitoring board (DSMB) then assessed the data and identified no increased risk of thrombosis among the 21,583 participants receiving at least one dose of the vaccine, as well as no risk of cerebral venous sinus thrombosis (CVST), the specific type of brain blood clot that has been of concern in Europe.

In response to a number of European countries suspending use of the vaccine while investigations are conducted, the European Medicines Agency (EMA) stated on 11 March: “There is currently no indication that vaccination has caused these conditions, which are not listed as side effects with this vaccine.

"The vaccine's benefits continue to outweigh its risks and the vaccine can continue to be administered while investigation of cases of thromboembolic events is ongoing.”

Medical experts have highlighted that there is always a risk of side effects when being treated or vaccinated against an illness, but these are usually minor and treatable.

A spokesperson for the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) said: "Given the large number of doses administered, and the frequency at which blood clots can occur naturally, the evidence available does not suggest the vaccine is the cause.”

What are the side effects of the AstraZeneca vaccine?

The UK government has highlighted on its website that there are often some minor side effects of any vaccine.

The government stated that in clinical trials for the Oxford AstraZeneca vaccination, these were “mostly mild to moderate in nature and resolved within a few days with some still present a week after vaccination.”

The following side effects occurred in clinical trials:

Very Common (may affect more than 1 in 10 people):

tenderness, pain, warmth, itching or bruising where the injection is given generally feeling unwell feeling tired (fatigue) chills or feeling feverish headache feeling sick (nausea) joint pain or muscle ach

Common (may affect up to 1 in 10 people):

swelling, redness or a lump at the injection site fever being sick (vomiting) or diarrhoea flu-like symptoms, such as high temperature, sore throat, runny nose, cough and chills

Uncommon (may affect up to 1 in 100 people):

feeling dizzy decreased appetite abdominal pain enlarged lymph nodes excessive sweating, itchy skin or rash

Not known (cannot be estimated from the available data):

severe allergic reaction (anaphylaxis)

Which European countries have stopped using it?

Some European countries have temporarily suspended the use of the Oxford AstraZeneca vaccine after raising concerns over the risk of blood clots in patients who have received a dose.

France, Germany and Spain are the latest to join a list of EU countries who have announced they will not use the vaccine until further investigations have been conducted.

This change in approach comes just five days after France and Germany said they would continue to roll out the AstraZeneca vaccine. "The benefits... are higher than the risks," French Health Minister Olivier Véran said.

Ireland has also suspended use of the vaccine, while Northern Ireland continues to administer doses.

Stephen Donnelly, Ireland's Health Minister, said he was hopeful that the suspension was "nothing more than a very short deferral".

Dr Ronan Glynn, Ireland's deputy chief medical officer, said the country took the decision to stop using the vaccine after new information was received from the Norwegian Medicines Agency.

He added that while there is no conclusion that there's a link to the AstraZeneca vaccine, the decision to suspend the vaccine programme came from "an abundance of caution".

Denmark, Norway and Iceland have also taken this approach to the rollout of the AstraZeneca vaccine, although Denmark has not published details about the deaths they have reported.

Following Denmark’s suspension, the EMA said the decision was a "precautionary measure [taken] while a full investigation is ongoing into reports of blood clots in people who received the vaccine, including one case in Denmark where a person died".

Other countries have stopped using certain batches of the drug in the meantime.

Austria, Estonia, Latvia, Lithuania and Luxembourg have suspended the use of the same batches of the vaccine, but continue to use other batches of the vaccine.

One Austrian woman died from "severe blood coagulation problems", 10 days after receiving the vaccine - but no clear link has been made between the administration of her jab and her death - a full inquiry is ongoing.

Italy has suspended the use of different batches, while Romania has suspended use of 4,200 doses from the same batch of vaccines as Italy.

Italy's medicines body said its decision was "precautionary", adding that no link had been established between the vaccine and subsequent "serious adverse events".

Two Italians are thought to have died shortly after receiving the vaccine.

All the countries that have suspended the use of specific batches or the use of any AstraZeneca jabs have described their actions as “precautionary”.

What is the efficacy rate of the Oxford AstraZeneca vaccine?

Following data released on 2 February, evidence now suggests a single dose of the Oxford Astrazeneca vaccine is 76 percent effective in preventing infection between 22 days and 90 days post-injection, rising to 82.4 per cent after a second dose at that stage.

The UK government continues to specify that there should be a 12-week period between the vaccines, as the study by Oxford University found that the vaccine is more effective overall if the second dose is delayed from 28 days until 90 days.

Will the UK continue to use the Oxford AstraZeneca vaccine?

The MHRA determines which vaccines are safe to use and the government follows this guidance when purchasing doses of the vaccine.

At present, the MHRA has raised no concerns about this vaccine and the Joint Committee on Vaccination and Immunisation (JCVI) continues to map out who is eligible for its vaccine.

The NHS has already rolled out over 11 million doses of the AstraZeneca vaccine and a further six million have been distributed across the EU.

A total of 15 events of deep-vein thrombosis (DVT) and 22 events of pulmonary embolism have been reported among those vaccinated, across the UK and EU.

Prof Adam Finn, a member of the JCVI, said: "If clear evidence of serious or life threatening side-effects emerges that will have important consequences.

"However so far it hasn't and it's highly undesirable to disrupt a complex and urgent programme every time people develop illnesses after receiving a vaccine that may be coincidental and not causally related."

AstraZeneca’s chief medical officer, Ann Taylor, said: "Around 17 million people in the EU and UK have now received our vaccine, and the number of cases of blood clots reported in this group is lower than the hundreds of cases that would be expected among the general population."

Phil Bryan of the MHRA, urged people invited to get their vaccine should continue to do so.