Explainer: Why have some countries suspended use of the AstraZeneca Covid-19 vaccine?
SINGAPORE — Several countries have suspended the roll-out of the AstraZeneca Covid-19 vaccine amid safety concerns relating to blood clotting, deep vein thrombosis and pulmonary embolism, which is a blockage of arteries in the lungs.
- There have been isolated reports of illnesses, mainly involving blood clots, along with some deaths, after people had received the AstraZeneca vaccine
- Numerous countries have temporarily halted roll-outs as a precautionary measure
- There is no evidence that these cases were caused by the vaccine based on reviews and reports, AstraZeneca and the WHO say
- They say the incidence of blood clots and similar conditions is no higher among those who got the vaccine than in the general population
SINGAPORE — Several countries have suspended the roll-out of the AstraZeneca Covid-19 vaccine amid safety concerns relating to blood clotting, deep vein thrombosis and pulmonary embolism, which is a blockage of arteries in the lungs.
Some countries including Denmark, Norway, Spain, Ireland and Indonesia temporarily halted use of the vaccine, while others such as Austria, Estonia, Latvia and Romania suspended specific batches.
However, AstraZeneca and the World Health Organization (WHO) have said that there is no evidence so far that these medical episodes were caused by the vaccination, and that the vaccine should continue being used.
The AstraZeneca vaccine has not been approved for use in Singapore.
Here is a timeline of the events so far and what experts have had to say.
WHERE HAS IT BEEN AUTHORISED?
Developed by Oxford University and British biotechnology firm Vaccitech, the AstraZeneca Covid-19 vaccine began Phase 1/2 trials in the United Kingdom in April last year.
The vaccine has since been granted conditional marketing authorisation or emergency use in more than 70 countries across six continents.
Its first authorisation was by the UK Medicines and Healthcare products Regulatory Agency on Dec 30 last year, with inoculations beginning in the country on Jan 4. The vaccine requires two doses given four to 12 weeks apart.
The AstraZeneca vaccine went on to receive conditional marketing authorisation by the European Medicines Agency (EMA) on Jan 29 for use in the European Union (EU), and was granted emergency use listing by the WHO on Feb 15.
WHICH COUNTRIES HAVE SUSPENDED USE, AND WHY?
The first incident that raised concerns about the AstraZeneca vaccine was on March 7, with Austria suspending the use of one batch of the vaccine following the death of a 49-year-old woman due to “severe coagulation disorders”.
A 35-year-old woman also developed a pulmonary embolism, which is an acute lung disease caused by a dislodged blood clot.
On March 11, Denmark, Norway and Iceland followed with the suspension of use of the AstraZeneca vaccine after a 60-year-old Danish woman suffered a blood clot and subsequently died. She had received the shot from the same batch as the one in Austria.
Separately, Italy said it would suspend use of a different AstraZeneca batch after two people died in Sicily.
One was a 43-year-old man who died of a suspected heart attack and the other, a 50-year-old man, was diagnosed with a deep vein thrombosis which led to brain haemorrhage.
On March 12, Bulgaria suspended its use of the AstraZeneca vaccine after a 57-year-old woman — who had a history of heart disease and suffered from obesity — suffered from "acute suffocation" and is suspected to have died from heart failure.
The following day, Norway reported that three people under the age of 50 had been hospitalised for bleeding, blood clots and a low count of blood platelets.
Then, on March 14, Denmark reported “highly unusual” symptoms in a 60-year-old woman who died from a blood clot after receiving the vaccine.
Other countries that have joined in the suspension of the AstraZeneca vaccine or one of its batches are: Estonia, Latvia, Lithuania, Luxembourg, Spain, Germany, Italy, France, the Netherlands, Cyprus, Portugal, Slovenia, Ireland, Romania, Sweden, Latvia and Indonesia.
Meanwhile, countries such as Thailand, the UK and Australia are continuing with AstraZeneca vaccinations.
WHAT SYMPTOMS HAVE PEOPLE EXPERIENCED?
The majority of health incidents relate to blood clots, which are clumps of blood that often form when a blood vessel is damaged. They may obstruct blood flow, potentially blocking flow to the heart, brain or other organs.
Blood clots can therefore lead to serious medical problems such as deep vein thrombosis and pulmonary embolism, two symptoms that have also been reported in previous cases.
On Tuesday (March 16), the New York Times reported that blood clots are common in the general population, and health authorities suspect that the reported cases are likely coincidental and therefore not related to the vaccination.
“There are a lot of causes of blood clotting, a lot of predisposing factors, and a lot of people who are at increased risk — and these are often also the people who are being vaccinated right now,” the New York Times quoted vaccine researcher at Oregon Health and Science University, Dr Mark Slifka, as saying.
WHAT HAVE ASTRAZENECA AND THE WHO SAID?
On Sunday, AstraZeneca said a review of safety data — covering more than 17 million people vaccinated in the EU and the UK — “showed no evidence of an increased risk of pulmonary embolism, deep vein thrombosis or thrombocytopenia”.
The drugmaker said that as of March 8, 15 events of deep vein thrombosis and 22 events of pulmonary embolism had been reported, numbers that are similar across other licensed Covid vaccines.
“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,” it said.
Additional tests are being conducted, and there have been no causes for concern so far. The monthly safety report will be made public on the EMA website in the following week, it added.
Both the EMA and the WHO have said there is no indication that the health events were caused by the vaccination.
On Monday, the WHO urged countries not to pause vaccination campaigns.
"As of today, there is no evidence that the incidents are caused by the vaccine and it is important that vaccination campaigns continue so that we can save lives and stem severe disease from the virus,” WHO spokesman Christian Lindmeier said.
The WHO said its advisory panel was reviewing reports and once findings are available, they will be communicated to the public.
WHAT DOES THIS MEAN FOR SINGAPORE?
At the moment, only the Pfizer-BioNTech and Moderna vaccines have been authorised for use in Singapore.
A third vaccine — China’s Sinovac — arrived here last month, but has yet to be authorised.
Singapore’s Health Sciences Authority (HSA) told TODAY that it has been in talks with various companies — including AstraZeneca — on their submission plans for Covid-19 vaccines.
“All vaccines are rigorously evaluated by HSA on their quality, safety and efficacy before they are approved for use in Singapore,” it added.
Unlike the Pfizer-BioNTech and Moderna vaccines, the AstraZeneca vaccine does not rely on messenger RNA (mRNA) technology, and therefore does not have to be kept at ultra-low temperatures like those two vaccines.