Explained: why some countries have suspended the use of the AstraZeneca vaccine

NEW DELHI: Several countries have suspended or delayed the deployment of the Covid-19 vaccine developed by the University of Oxford-AstraZeneca following reports of blood clots in some people.
Thailand is the latest country to delay use of the UK-based vaccine after health officials in Denmark, Norway and Iceland suspended injections on Thursday.
Austria earlier stopped using a batch of AstraZeneca injections while investigating a death from bleeding disorders and disease from pulmonary embolism.
‘Blood clots’
Denmark initially suspended injections for two weeks after a 60-year-old woman, who was injected with AstraZeneca from the same batch used in Austria, formed a blood clot and died, have said the Danish health authorities.
Their response was also prompted by reports of “possible serious side effects” from other European countries.
“It is currently not possible to conclude that there is a link. We are acting early, this needs to be fully investigated,” Health Minister Magnus Heunicke said on Twitter.
Iceland suspended injections with the vaccine on Thursday pending the results of an EMA investigation. Italy, also on Thursday, announced that it would suspend the use of a different AstraZeneca batch than the one used in Austria.
Four other countries – Estonia, Lithuania, Luxembourg and Latvia – have stopped inoculations of the batch while investigations continue, the EMA said.
Little evidence
Some health experts said there was little evidence to suggest that the AstraZeneca vaccine should not be given and that blood clot cases matched the rate of such cases in the general population.
“The problem with spontaneous reports of suspected adverse reactions to a vaccine is the enormous difficulty in distinguishing a causal effect from a coincidence,” Stephen Evans, professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine, told Reuters .
European medicines regulator EMA said the benefits of the vaccine outweighed its risks and could continue to be administered.
AstraZeneca told Reuters in a written statement that the safety of its vaccine has been extensively studied in human trials and peer-reviewed data has confirmed that it is generally well tolerated.
Other experts have pointed out that of the millions of AstraZeneca vaccines given elsewhere, including Britain, there have been no reported cases of the vaccine causing blood clots or related problems.
Australia and Canada continue to deploy
At the same time, Australia announced on Friday that it would continue to deploy AstraZeneca’s Covid-19 vaccine as there was no evidence of a link to blood clots.
The Australian government has said that while its drug regulatory body monitors these cases, there will be no pause in vaccine rollout.
“We are continuing with the vaccine, we are continuing the deployment,” Deputy Prime Minister Michael McCormack told reporters in Melbourne.
Canada also said the AstraZeneca vaccine was safe after Denmark and Norway temporarily suspended its use.
“Health Canada is aware of reports of adverse events in Europe following immunization with the AstraZeneca Covid-19 vaccine, and wishes to reassure Canadians that the benefits of the vaccine continue to outweigh its risks,” the health ministry said in a statement.
“At the moment, there is no indication that the vaccine caused these events,” he said.
Mexico has also said it will continue to apply doses of the AstraZeneca vaccine.
Swedish authorities said they had not found sufficient evidence to stop vaccination with the AstraZeneca vaccine.