Thailand is the latest country to delay the use of the UK-based vaccine after health authorities in Denmark, Norway and Iceland suspended shots on Thursday.
Austria previously stopped using a batch of AstraZeneca injections during the investigation of a death from coagulation disorders and a disease from a pulmonary embolism.
‘Blood clots’
Denmark first suspended the shots for two weeks after a 60-year-old woman, who received an AstraZeneca injection from the same batch used in Austria, formed a blood clot and died, Danish health authorities said.
Their response was also prompted by reports “of possible serious side effects” from other European countries.
“It is currently not possible to conclude whether there is a link. We are taking early action, it needs to be thoroughly investigated,” Health Minister Magnus Heunicke said on Twitter.
Iceland suspended the vaccine on Thursday pending the results of an investigation by the EMA. Italy also said on Thursday that it would suspend the use of a different AstraZeneca batch from the one in Austria.
Four other countries – Estonia, Lithuania, Luxembourg and Latvia – have halted the batch’s vaccinations while the investigation continues, the EMA said.
Little evidence
Some health experts said there was little evidence to suggest that the AstraZeneca vaccine should not be administered and that blood clot cases were consistent with the percentage of such cases in the general population.
“The problem with spontaneous reports of suspected adverse reactions from a vaccine is the tremendous difficulty in distinguishing a causal effect from chance,” said Stephen Evans, professor of pharmaco-epidemiology at the London School of Hygiene & Tropical Medicine.
The European medical regulator EMA said the benefits of the vaccine outweighed the risks and could be administered further.
AstraZeneca told Reuters in a written statement that the safety of its vaccine had been extensively studied in human trials and peer-reviewed data confirmed that it was generally well tolerated.
Other experts have pointed out that of the millions of AstraZeneca vaccine injections administered elsewhere, including in the UK, no cases have been reported where the vaccine caused blood clots or related problems.
Australia, Canada to continue the rollout
Meanwhile, Australia said on Friday that AstraZeneca’s Covid-19 vaccine will continue to roll out as there was no evidence of a link to blood clots.
The Australian government said that while the pharmaceutical regulator was monitoring those cases, there would be no pause in the vaccine rollout.
“We will continue with the vaccine, we will continue with the rollout,” Deputy Prime Minister Michael McCormack told reporters in Melbourne.
Canada also said the AstraZeneca vaccine is safe after Denmark and Norway temporarily discontinued its use.
“Health Canada is aware of adverse event reports in Europe following immunization with the AstraZeneca Covid-19 vaccine and wants to reassure Canadians that the benefits of the vaccine outweigh the risks,” the health department said in a statement.
“At the moment there is no evidence that the vaccine caused these events,” he said.
Mexico has also said it will continue to administer doses of the AstraZeneca vaccine.
Swedish authorities said they had found insufficient evidence to stop the vaccination with the AstraZeneca shot.