Denmark, Iceland and Norway have suspended the use of the Oxford-AstraZeneca Covid-19 vaccine while the European Union's medicines regulator investigates whether the shot could be linked to a number of reports of blood clots.

Denmark announced a two-week suspension on Thursday following a number of reports of clotting in the country, including one fatal case. Iceland and Norway followed suit, but did not say how long their suspensions would last.

Danish Health Minister Magnus Heunicke made clear the pause was a “precautionary measure,” saying it was not possible yet to draw conclusions.

“We act early, it needs to be thoroughly investigated,” he said in a tweet.

The Danish Health Authority also stressed that the decision was temporary.

“We are in the middle of the largest and most important vaccination rollout in Danish history. And right now we need all the vaccines we can get. Therefore, putting one of the vaccines on pause is not an easy decision. But precisely because we vaccinate so many, we also need to respond with timely care when there is knowledge of possible serious side effects. We need to clarify this before we can continue to use the vaccine from AstraZeneca,” Søren Brostrøm, director of the National Board of Health, said in the statement.

“It is important to emphasize that we have not opted out of the AstraZeneca vaccine, but that we are putting it on hold. There is good evidence that the vaccine is both safe and effective. But both we and the Danish Medicines Agency have to react to reports of possible serious side effects, both from Denmark and other European countries. It shows that the monitoring system works. ”

Speaking to CNN Kjartan Njálsson, assistant to the director of health in Iceland, said that although there had been no reports of patients developing blood clots in the country, they were waiting for advice from the European Medicines Agency (EMA). “It’s the lack of data right now that concerns us,” he added.

The EMA said later Thursday that it did not recommend suspending use of the vaccine.

The agency said it was aware that Denmark had suspended use but that there was “currently no indication that vaccination has caused these conditions, which are not listed as side effects with this vaccine.”

“The vaccine’s benefits continue to outweigh its risks and the vaccine can continue to be administered while investigation of cases of thromboembolic events is ongoing,” the agency added.

The EMA also noted that the number of blood clots seen in vaccine recipients was no higher than the rate among people who had not received the shot in Europe.

The Norwegian Institute of Public Health issued a statement saying the country had also chosen to “pause” inoculations following report of a death in Denmark as a result of a blood clot. It also noted there had been reported cases of blood clots shortly after receiving Covid-19 vaccinations in Norway but “mainly in the elderly where there is often another underlying disease as well.”

Earlier this week, a number of EU nations paused the use of doses that came from a particular batch of AstraZeneca vaccine, after a 49-year-old woman in Austria died of multiple thrombosis on Sunday. The EMA said Wednesday there was “no indication” that vaccination had been behind the cases of clotting or death.

AstraZeneca defends shot’s safety

In a statement on Thursday, AstraZeneca said that patient safety was its “highest priority.”

“Regulators have clear and stringent efficacy and safety standards for the approval of any new medicine, and that includes COVID-19 Vaccine AstraZeneca. The safety of the vaccine has been extensively studied in Phase III clinical trials and peer-reviewed data confirms the vaccine is generally well tolerated,” the company said in a statement.

In the UK, the Medicines and Healthcare products Regulatory Agency (MHRA) said Danish authorities had taken a “precautionary measure” and advised people to still take their vaccine when instructed to.

Spain’s health minister Carolina Darias called for calm on Thursday. “I would to send a message of calm and caution. In Spain we have not been notified of any case related to blood clots,” Darias told local TV station La Sexta. The Dutch health minister also said there was no reason to stop using the vaccine.

“Our experts say there is no cause for concern, we can simply continue vaccinating,” Hugo de Jonge said Thursday.

On Thursday, Italy joined Austria, Estonia, Lithuania, Luxembourg and Latvia in suspending the use of doses from batch ABV5300. Danish officials did not specify whether its reported death was connected to the same batch.

The EMA said that batch ABV5300 had been delivered to 17 EU countries, comprising 1 million doses of the vaccine.

“Some EU countries have also subsequently suspended this batch as a precautionary measure, while a full investigation is ongoing. Although a quality defect is considered unlikely at this stage, the batch quality is being investigated,” EMA said in a statement.

The investigation is the latest trouble in Europe for British-Swedish drugmaker AstraZeneca, which has come under pressure to produce more vaccines after it fell tens of millions of doses short in deliveries to the European Union.

Italy banned the export of 250,000 doses of the vaccine to Australia last week in an effort to protect its national supplies. France said it would also consider banning exports, as concerns of vaccine nationalism rise.

The company has also faced resistance in the bloc, where regulatory bodies in member countries have been slow or hesitated to recommend the vaccine in people over the age of 65, citing a lack of data.

Regulatory bodies in several countries, including Germany and France, have since changed recommendations to include over-65s as real-world data has since shown that the AstraZeneca vaccine is highly effective at preventing hospitalization in older populations. France limits the shot to people under the age of 74.

Anecdotal reports suggest people in some EU countries, however, are still choosing not to take the AstraZeneca vaccine.