World Clot questions over AstraZeneca and J&J vaccine
Decision about AstraZeneca's use in Australia to be make this week
An urgent investigation was launched into the potential side effects of the Covid-19 vaccine after a Melbourne man who received the jab was hospitalised with a rare blood clotting condition. Experts have been holding talks with European regulators to determine whether the 44-year-old's low blood platelets and 22 other similar cases in the UK are linked to the vaccine. The Australian Technical Advisory Group on Immunisation (ATAGI) will convene on Wednesday to weigh up the risks and benefits of AstraZeneca jabs once further information is provided from international discussions.
The AstraZeneca and Johnson & Johnson vaccines have come under suspicion of causing very rare but serious blood clots in a handful of cases among the millions vaccinated in the drive to bring the pandemic under control.
Here is what we know about the two vaccines, which are based on the same technology.
- What happened? -
The European Medicines Agency last week said unusual blood clots should be listed as a very rare side effect of the AstraZeneca vaccine, although stressing that overall benefits in preventing Covid-19 outweighed the risks.
AstraZeneca vaccine: what we know and don't know
A European Medicines Agency (EMA) recommendation Wednesday that a dangerous type of blood clot should be listed as a "very rare side effect" of the AstraZeneca jab stopped just short of saying there is a causal link between the vaccine and the deadly condition. "The reported combination of blood clots and low blood platelets is very rare, and the overall benefits of the vaccine in preventing COVID-19 outweigh the risks of side effects," theQuestions have persisted for weeks on whether highly unusual blood clots among those getting the AstraZeneca vaccine against Covid-19 were more frequent than in the general population, and what causes them if they were.
The clots occur in veins in the brain -- called cerebral venous sinus thrombosis, CVST -- as well as the abdomen and arteries.
They are uncommon both for where they appear in the body and because they occur together with low levels of blood platelets, which help the blood to clot.
Paradoxically, this can mean the patient has both haemorrhages as well as blood clots.
There were 222 cases of these atypical thromboses out of 34 million AstraZeneca injections carried out in the European Economic Area (EU, Iceland, Norway, Liechtenstein) and Britain, as of April 4, according to the EMA. And there were 18 deaths, as of March 22.
Young Australians' hopes for an overseas holiday could be dashed
Australia had been aiming to open its international borders beyond New Zealand from the end of October when every citizen was expected to receive at least their first vaccine dose. But that timeline is now almost impossible to meet following Thursday's announcement the AstraZeneca Covid-19 vaccine - which Australia had purchased the most doses of - was no longer recommended for under 50s, only the Pfizer jab.
Most of the cases reported were in women under 60 years of age within two weeks of vaccination.
In the US, where more than 6.8 million single-shot J&J vaccine shots have been administered, health authorities on Tuesday recommended that use of the jab be paused while they investigate six reported cases of CVST that also occurred with low levels of blood platelets.
All those cases involved women between the ages of 18 and 48 and one case was fatal, officials said.
- Suspected causes -
Both of these vaccines -- as well as the Russian Sputnik V jab -- are based on a technique known as "viral vector".
The vaccines use a common-cold causing adenovirus, modified so it can't replicate, as a "vector" to shuttle genetic instructions into human cells, telling them to create a protein of the coronavirus.
This trains the immune system to be ready for the live coronavirus
AstraZeneca opted for a chimpanzee adenovirus, J&J for a human adenovirus.
Here's why the AstraZeneca COVID vaccine is recommended for over 50s but not other Australians
But if you're wondering what Australia's vaccine changes mean for you, or whether it's still safe to take the AstraZeneca vaccine, here's what the expert advice is saying.With the government accepting advice that the small risk of blood clots associated with the AstraZeneca vaccine means it should not be given to people under 50, its plan to vaccinate Australians against the virus is in disarray.
"Whilst a causal link between certain Covid-19 vaccinations, platelet abnormalities and blood clots has not, so far, been confirmed, the index of suspicion is rising that these rare cases may be triggered by the adenovirus component of the AstraZeneca and J&J vaccines," said Eleanor Riley, an immunology professor at Edinburgh University.
- What mechanism? -
Although nothing has been proven, Peter Marks of the US Food and Drug Administration said the "probable cause" of the clots could be an unusual reaction to the vaccines.
The FDA has also said that while in normal circumstances an anticoagulant drug called heparin is used to treat these blood clots, in this case administering heparin may be dangerous.
That might be because the disorder resembles a rare reaction to heparin itself, in which the body forms antibodies in response to the thinner, and in turn triggers platelets to form dangerous clots.
A team of German and Austrian scientists made the connection between this previously-known immune response to heparin and the AstraZeneca vaccine in March.
Karl Stefanovic says he is nervous about getting the AstraZeneca jab
Today host Karl Stefanovic, 46, said on Monday he would preference waiting for an alternative vaccine such as Pfizer over being administered doses of the AstraZeneca jab.Stefanovic, 46, said on Monday he would preference waiting for an alternative vaccine such as Pfizer over being administered doses of the AstraZeneca jab, when speaking to Professor Kristine Macartney.
And the EMA said this was "one plausible explanation", calling for more research.
- Balancing risk -
The European agency has said no specific risk factors for this type of reaction have been confirmed for the AstraZeneca vaccine, but different countries have opted to restrict access to the jab by age.
The reasoning is that the older people get, the more they risk developing a serious form of Covid, and the more it is in their interest to be vaccinated, despite potential side effects.
For example, Britain has said it will not administer AstraZeneca to the under 30s, while France is not using it on the under 55s.
In the US, health authorities said the suspension of the J&J vaccine was "out of an abundance of caution".
People who have had the shot within the past three weeks were asked to report to their doctors if they experience severe headaches, abdominal pain, leg pain, or shortness of breath.
Ian Douglas, Professor of Pharmacoepidemiology at London School of Hygiene & Tropical Medicine, said it was important to underscore how rare these events appear to be.
"To put this into perspective, it's similar to the chance of being struck by lightning in any given year in the UK," he told the Science Media Centre in response to the US announcement.
"On the other hand, the risks from Covid-19 are substantial."
Family speaks out after loved one died after receiving Covid vaccine .
Genene Norris, 48, from the New South Wales Central Coast died on April 14 after receiving the embattled coronavirus jab on April 8. She developed blood clots the next day and four days after she received the jab she was placed on dialysis in an intensive care unit until her death.The Therapeutic Goods Administration's vaccine safety investigation found Ms Norris' case of thrombosis is likely to be linked to the vaccine.