Denmark has become the first European country to discontinue the use of the Oxford University AstraZeneca COVID-19 vaccine on Tuesday, April 14, citing alleged unusual but dangerous side effects.

“Denmark’s vaccination campaign will go ahead without the AstraZeneca vaccine,” Health Authority director Soren Brostrom said at a news conference, despite the WHO and European medicines watchdog advice to continue using it, reports The Guardian.

Denmark’s decision came amid a growing emphasis on unusual side effects, with the U.S.-produced Johnson & Johnson vaccine halted in the United States due to related issues.

The halt of AstraZeneca vaccine in Denmark will possibly delay the EU’s vaccination effort by several months.

In Europe, Sweden also announced that it would halt its own rollout of a second vaccine made by Johnson & Johnson, which has been attributed to rare blood clots as well. It is to be resumed however, and given only to those over 65 years of age. There have been few reported serious cases of side effects in older people.

Finland has stated that it would continue to restrict the AstraZeneca vaccine to those aged 65 and over, saying that a second dose from another manufacturer might be given. It was working on a roadmap to continue vaccines.

The European Medicines Agency (EMA) said in a statement on April 7 that there is a “possible association” between unusual blood clots and the vaccine and that it is “reminding healthcare practitioners and people getting the vaccine to be mindful of the risk of very rare cases of blood clots associated with reduced blood platelet levels arising within 2 weeks of vaccination.”

“The majority of the cases recorded so far have occurred within two weeks of vaccination in women under 60 years old. Clear risk factors have not been proven based on publicly available evidence,” it said.

According to Danish authorities, the decision to suspend AstraZeneca’s vaccine would push back the end of Denmark’s vaccination program from July 25 to early August. Denmark is also using the Pfizer/BioNTech vaccine, manufactured in the United States, and each person needs two doses.

Before this week’s decision, Brostrm said last month that Denmark had “followed a precautionary principle” for it.

After warnings of sporadic yet critical cases of blood clots in those who had been administered the vaccine, Denmark suspended the AstraZeneca vaccine’s use in its vaccination rollout.

More than 140,000 people in Denmark have got the Anglo-Swedish drugmaker’s vaccine so far, and two cases of thrombosis were attributed to vaccines.

Just 8% of the country’s 5.8 million people have been completely vaccinated against Covid-19, while 17% have received the first dose.