Denmark halted the use of the Oxford-AstraZeneca Covid-19 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 use of a particular batch of the drug because a woman died 10 days after taking it. Estonia, Norway, Latvia, Lithuania and Luxemburg have also stopped using the batch.
Danish authorities said they were pausing 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.