Denmark has temporarily halted the use of the Oxford-AstraZeneca vaccine as a precaution, after reports of a small number of blood clots and one death.
The Danish health authority said it was too early to say whether there was a link to the AstraZeneca vaccine.
Austria earlier stopped using a batch of the drug, prompting the EU medicines agency to say there was no indication the vaccine caused blood clots.
The company says its safety has been studied extensively in clinical trials.
“Patient Safety is the highest priority for AstraZeneca,” a spokesperson said.
“Regulators have clear and stringent efficacy and safety standards for the approval of any new medicine, and that includes Covid-19 Vaccine AstraZeneca.”
Peer-reviewed data confirmed it had been “generally well tolerated”, the statement added.
The Danish decision came days after Austria suspended the use of a particular batch of the drug because a woman died 10 days after taking it. Estonia, Latvia, Lithuania and Luxemburg have also stopped using the batch.
Danish authorities said they were pausing the use of the vaccine for 14 days in what Health Minister Magnus Heunicke called a “precautionary measure”.
Although no link had been established, he said “we must respond in a timely and careful manner” until a conclusion was reached.
The decision to put the vaccine on hold in Denmark and Austria is a setback for a European vaccination campaign that has stuttered into life, partly due to delays in delivery of the AstraZeneca drug.
The Danish authority said it was not an easy decision as it was during the biggest and most important rollout in the country’s history.
The EU medicines agency EMA said its safety committee was reviewing the Austrian case, but made clear that “there is currently no indication that vaccination has caused these conditions, which are not listed as side effects with this vaccine”.
The number of “thromboembolic events in vaccinated people is no higher than that seen in the general population”, it added.
Officials say they have received reports of fatal or life-threatening blood clots in a small number of people who had recently received a dose of the Oxford-AstraZeneca vaccine. That may sound worrying, but it is not yet known if there is any connection between the two things.
It was on Sunday that a 49-year-old woman in Austria died from multiple blood clots. She had been vaccinated 10 days earlier. Another person who received a shot from the same vaccine batch was also hospitalised for a blood clot in the lung.
As of 9 March 2021, two other reports of thromboembolism have been received for this batch, ABV5300. It contained a million doses and was delivered to 17 EU countries, including Austria and Denmark.
A full investigation into batch quality is ongoing, but a defect is considered unlikely.
Overall, 22 cases of thromboembolic events have been reported among the three million people vaccinated with the AstraZeneca vaccine in the European Economic Area.
Any approved treatment, including vaccines, carries a risk of some side effects for some people, but most are usually mild and severe ones are rare.