Which countries have paused their use of the Oxford/AstraZeneca vaccine?
A host of European countries have put all vaccinations with this jab on hold, including Germany, France, Spain, Italy, Denmark, Norway and Ireland. Some others such as Estonia and Austria have suspended vaccinations from particular batches of the vaccine.
Why have the vaccinations been paused?
A small number of isolated cases of blood-clotting conditions among those who have received the vaccine have been reported in some countries. These include pulmonary embolism and deep vein thrombosis as well as rarer conditions such as thrombocytopenia, where people do not make enough platelets, and a disorder called cerebral venous sinus thrombosis (CVST), which is a type of blood clot in the brain.
European governments say they are acting out of “an abundance of caution”, pausing vaccinations while the cases are investigated. The European Medicines Agency (EMA) has said it expects to report its conclusions on Thursday.
Are these events down to the vaccine?
That’s what the investigations are looking into, but leading bodies have stressed that evidence is so far lacking.
Emer Cooke, the head of the EMA, said on Wednesday that there was no indication that the case have been caused by the jab, and that the EMA remains “firmly convinced” the benefits of the jab outweigh the risks. But, she added, the cases “are a serious concern and need serious and detailed scientific evaluation”.
Prof Anthony Harnden, the deputy chair of the UK’s Joint Committee on Vaccination and Immunisation (JCVI), said: “The UK has administered 11m doses of the AstraZeneca vaccine and there has been no demonstrable difference in the number of blood clots since the vaccine was introduced.”
Dr Phil Bryan, vaccines safety lead at the UK’s Medicines and Healthcare products Regulatory Authority, agreed. “We are closely reviewing reports but the evidence available does not suggest the vaccine is the cause,” he added.
How is this being investigated?
One way is to look at whether the incidence rate of cases of a certain condition is higher among those who have had the vaccine than would be expected from typical rates.
On Tuesday, Germany’s federal ministry of health said that there had been seven cases of CVST, including three deaths, in the 1.6 million people who had received the jab. That, it said, means that the rate of CVST was three or four times higher that would normally be expected.
But Prof Jon Gibbins, director of the Institute for Cardiovascular and Metabolic Research at the University of Reading, told the Hlcarpenter.com that getting accurate information on whether rare forms of clotting might be slightly elevated was tricky.
“It is quite hard to diagnose something in a very precise manner if it is very uncommon,” he said.
Indeed Gibbins noted that there are different estimates for the background, or typical, rate of CVST– although all show that it is rare, with the higher estimates suggesting a rate of 15-16 cases per million per year.
Paul Hunter, professor in medicine at the University of East Anglia, said the rates from Germany among those vaccinated with the AstraZeneca jab, of about seven cases of CVST in 1.6 million people vaccinated so far, while raised, is not significantly higher than these estimates, suggesting that it is possible that they have nothing to do with the vaccination.
“I would certainly not call it striking when it is still likely to be a random issue,” he said.
Are these blood clotting problems more common among particular groups?
That is still being looked at, but the German federal ministry of health has said that young people, especially young women, seem to be overrepresented in cases of cerebral sinus venous thrombosis among those who have been vaccinated.
Hunter, however, urged caution. “[CVST] is also more common in people under 50 years old than in people over 50 years old, and a little more common in women than in men,” he said.
If the rate is truly higher among those who have had the jab, does that mean the cases were caused by the vaccination?
Not necessarily. Hunter notes that even if there has been a true rise in unusual conditions among the vaccine recipients, that does not mean they are caused by vaccination: the rate could be inflated because people are looking harder for cases.
Should rollout of vaccinations with the Oxford/AstraZeneca jab have been paused?
Germany thinks so, saying it would not have been justifiable to keep vaccinating until the potential link has been tested. But the World Health Organization has urged countries to continue using the vaccine while the cases are investigated.
Hunter said that while cases should be investigated, the UK is right not to put use of the jab on hold. “I think the UK has taken the approach that will ultimately lead to fewer deaths,” he said. “I would not have argued for pausing vaccination given the tenuous nature of the evidence currently available.”
Indeed, with a third wave of coronavirus infections sweeping across the EU, vaccination has become an even more pressing matter.
As Gibbins points out, the chance of death for a man in their mid-forties infected with Covid is much higher than the chance of CVST. “The death rate [from Covid] is about 0.1%, that’s 1,000 deaths per million.”