AstraZeneca blood clot cases: What we know and what’s next

Australia will continue its inoculation program with AstraZeneca PLC, health officials said on Saturday, despite a blood clotting case of a 44-year-old man who was admitted to a Melbourne hospital with clotting, just days after receiving the AstraZeneca vaccine.

The UK medical regulator also said on Saturday, local time, that out of 30 people who suffered rare blood clots after receiving the AstraZeneca vaccine, seven had died.

It comes as several European countries paused the jab over a potential link to blood clots.

As of 31 March, The European Medicines Agency (EMA) identified 62 cases of cerebral venous sinus thrombosis (CVST) - 44 of them in Europe - among 9.2 million given doses of AstraZeneca.

Here is some helpful information surrounding the Oxford-AstraZeneca vaccine:

What is the AstraZeneca vaccine, and how does it work?

The AstraZeneca vaccine is a viral vector vaccine for COVID-19 developed by Oxford University and AstraZeneca.

It uses the modified common cold virus (known as adenovirus ChAdOx1) found in chimpanzees.

This is a harmless, weakened adenovirus that has been genetically changed so that it is impossible for it to grow in humans.

It has been modified to mimic coronavirus and once injected, triggers the body's immune system to fight off coronavirus virus, should it need to.

Where have blood clotting deaths occurred globally?

Seven people died in the UK after suffering cerebral sinus vein thrombosis (CSVT).

In addition to the UK's 30 cases and seven deaths, France has 12 cases and four deaths, and Norway has five cases and three deaths.

Germany reported 31 cases of CVST, and nine deaths out of the 2.7 million people vaccinated, with most cases in young or middle-aged women.

Which countries have paused or suspended AstraZeneca vaccine over blood clotting conditions/deaths now?

Austria

Suspended use of the vaccine on 7 March after the death of one person and illness of second person.

Cameroon

Suspended distribution of the vaccine it was scheduled to receive on 20 March 20 from COVAX due to international reports.

Canada

Suspended the jab for people under 55.

Denmark

Suspension of the vaccine occurred on 25 March for two weeks and has been extended by three weeks while further investigations are carried out.

Finland

Resumed using the vaccine from 29 March, but only for people 65 and over.

France

Resumed using AstraZeneca's vaccine on 19 March, but only for people 55 and older.

Georgia

Limited the use of the vaccine after a nurse died of anaphylactic shock.

Germany

Restricted use of the jab to people over 60 as of 31 March, following further reports of brain clots.

Indonesia

Resumed using the vaccine on 22 March 22 but recommended against using the jab in people with a low blood platelet count.

Italy

Paused using the vaccine on 19 March and resumed but people who refuse the jab will be given another option later.

Lithuania

Resumed administering the vaccine on 19 March but only for people over 65.

North Macedonia

On 31 March the jabs were restricted to people aged over 60.

Norway

Norway will decide on 15 April whether or not it will be using the vaccine.

Romania

Stopped vaccinating people on 11 March.

Sweden

Paused use of the vaccine but resumed use on 25 March for people 65 and older. Restrictions are in place for people under 65 years old.

Who is suffering from the blood clotting?

Many of the cases reported were in adults aged under 55 years, and the majority were in women.

This higher proportion might be because many frontline health care workers, who are often women, were vaccinated as a priority.

However, it is not yet clear if age and sex are risk factors across the board.

What is being done to investigate blood clot deaths?

In the UK, Dr June Raine, the chief executive of the MHRA, said: "The benefits … in preventing COVID-19 infection and its complications continue to outweigh any risks and the public should continue to get their vaccine when invited to do so."

Nevertheless, investigations are underway in the UK and EU to determine if the AstraZeneca vaccine is causing the very rare blood clots.

The European Union's medicines regulator (the EMA) said a connection was "not proven, but is possible".

But on 31 March, despite the reports of rare blood clots, EMA head Emer Cooke said there was "no evidence" that would justify stopping the use of AstraZeneca's vaccine in any demographic.

Meanwhile, at an emergency meeting in Germany, national Health Minister Jens Spahn and 16 state health ministers decided to suspend the routine use of the AstraZeneca vaccine for people under age 60.

Germans under 60 can still receive the shot at the discretion of doctors, and after individual risk analysis.

What have studies found out so far?

In a study released on 28 March that has not yet been peer-reviewed, German and Austrian researchers pointed to a known biological mechanism as a possible explanation for the apparent surge in atypical thrombosis.

The AstraZeneca vaccine, they wrote, is associated with a thrombosis disorder "that clinically resembles heparin-induced thrombocytopenia (HIT)".

The authors, led by Andreas Greinacher from the University of Greifswald, proposed a name for what they described as a new syndrome: "vaccine-induced prothrombotic immune thrombocytopenia (VIPIT)."

"We have to stop speculating on whether there is a link or not - all the cases showed these symptoms three to 10 days after inoculation with the AstraZeneca vaccine," Pal Andre Holme, who heads a team at Oslo National Hospital working on these cases, told Norwegian television. "We have not found any other triggering factor."

Researchers at Oslo National Hospital had earlier suggested that cases might have been triggered by a "powerful immune response" to the vaccine.

"We do not have just one vaccine, we have several," Sandra Ciesek, a professor of virology at Goethe University in Frankfurt, wrote in Science magazine.

"So, restricting the AstraZeneca vaccine to older people makes sense to me."

What does the WHO think about the blood clotting incidents?

The WHO released a statement acknowledging the temporary suspension of the jab in some EU countries based on reports of the rare blood coagulation reactions.

"Thromboembolic events are known to occur frequently. Venous thromboembolism is the third most common cardiovascular disease globally.

"In extensive vaccination campaigns, it is routine for countries to signal potential adverse events following immunisation. This does not necessarily mean that the events are linked to vaccination itself, but it is good practice to investigate them. It also shows that the surveillance system works and that effective controls are in place.

"WHO is in regular contact with the European Medicines Agency and regulators around the world for the latest information on COVID-19 vaccine safety. The WHO COVID-19 Subcommittee of the Global Advisory Committee on Vaccine Safety is carefully assessing the latest available safety data for the AstraZeneca vaccine. Once that review is completed, WHO will immediately communicate the findings to the public.

"At this time, WHO considers that the benefits of the AstraZeneca vaccine outweigh its risks and recommends that vaccinations continue."

Has Australia had a case involving blood clotting?

Yes, a 44-year-old Melbourne man developed thrombosis after receiving the jab.

Australia's Acting Deputy Chief Medical Officer Michael Kidd said it was "likely" there is a link between the AstraZeneca vaccine and a Melbourne man being hospitalised with blood clots.

Professor Kidd has said the national vaccination rollout for COVID-19 will not change. Picture: NCA NewsWire / Gary Ramage
Professor Kidd has said the national vaccination rollout for COVID-19 will not change. Picture: NCA NewsWire / Gary Ramage


What is Australia doing about it?

Professor Kidd has said the national vaccination rollout for COVID-19 will not change, but health authorities will continue to investigate whether blood clots developed by the Victorian man are linked to the AstraZeneca jab.

Prof Kidd told the media the Australian Technical Advisory Group on Immunisation (ATAGI) and the Therapeutic Goods Administration (TGA) had not recommended any change to the national vaccine plan following an urgent meeting of health authorities.

He cited a lack of definitive evidence of a connection between the man's condition and the vaccination he received in March.

However, he said that because the case was similar to those reported from overseas, a connection was likely.

"While at this time, we don't have evidence of causality, the clinical features of this case are consistent with what we have seen in international reports of similar cases. And it is likely that the case reported yesterday is related to the vaccine," Prof Kidd said.

The Therapeutic Goods Administration said on 31 March that a link between the vaccine and clot disorders had not been proven but that it was still investigating the issue as vaccinations continue.

A statement from ATAGI has been released for healthcare providers on the clotting,

providing information on clinical management.

What will happen next?

Given the small percentage of blood clot cases, unless a significant number of cases emerge, the jab will not be suspended.

It is up to each country to administer the doses or restrict them to certain types of people.

The European Medicines Agency (EMA) and the UK MHRA intend to provide updated information about their investigation into these cases some time in April.

The EMA is scheduled to meet on the question from April 6-9.

Originally published as AstraZeneca blood clot cases: What we know and what's next


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