Oxford-AstraZeneca has been forced to defend its Covid-19 vaccine after several European nations including Norway, Denmark, Iceland, Bulgaria and even Asian nation Thailand paused the roll out of the vaccine following reports it could be connected to blood clots.

Bulgaria joined Denmark, Norway and Iceland to suspend the use of the vaccine pending investigations into safety.

Bulgarian Prime Minister Boyko Borissov ordered a halt to all inoculation until the European Medicines Agency “rejects all doubts” about the vaccine’s safety, according to a government statement.

The move came in response to reports of blood clots in a few inoculated people in Denmark, including one fatality.

Thailand’s Prime Minister, Prayut Chan-o-cha, canceled plans to publicly get the AstraZeneca shot this weekend and the country also delayed its rollout.

“When there is an adverse event, we don’t need to be in rush,” said Piyasakol Sakolsatayadorn, a senior member of the country’s vaccination committee.

AstraZeneca has responded. In a statement the vaccine maker said there is “no evidence of an increased risk” of blood clots, and European and UK medicines regulators have each said the link between the vaccine and blood clots has not been confirmed and that rollouts should continue.

The Norwegian Institute of Public Health said the country has also reported cases of blood clots shortly after receiving a Covid-19 vaccination in Norway but “mainly in the elderly where there is often another underlying disease as well.”

Other countries, including Austria and Italy, have suspended specific batches of the vaccine.

The European Medicines Agency (EMA) has said that it did not recommend suspending use of the AstraZeneca vaccine, stating that there is “no indication” the vaccine caused the blood clots in the people who received the vaccine. The agency told countries they could keep rolling out the shot while investigations take place.

“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 said.

Health agencies of the UK, Germany, France, the Netherlands, Mexico and Nigeria are still administering the vaccine, saying it’s safe.