Danish health authorities decided Wednesday to permanently suspend the use of the AstraZeneca coronavirus vaccine amid concerns that it causes blood clots in rare cases.

Denmark became the first European country to abandon the vaccine altogether after temporary suspensions in Europe last month following the discovery of rare and sometimes fatal blood clots among a small number of people who had received it. Most countries have resumed vaccinating with the AstraZeneca shots, many of them with restrictions that it be used only on older people, who appear less at risk for the blood clots.

The Danish move was a signal of the depth of concerns about the vaccine’s side effects in at least some European countries, given that the virus continues to spread across Europe despite the ongoing vaccination campaign. Any delay in inoculations could lead to more cases and more deaths. Danish authorities said the decision to stop using the AstraZeneca vaccine will probably delay their efforts by several weeks.

“Our overall assessment is there is a real risk of severe side effects associated with using the COVID-19 vaccine from AstraZeneca,” Danish Health Authority Director General Soeren Brostroem said in a statement. “In the midst of an epidemic, it has been a difficult decision” to stop using the vaccine, he said.

But he said that Danish authorities believe they have the virus under control and that the oldest people most at risk of severe illness from covid-19, the disease caused by the virus, already have been vaccinated, so the government has the flexibility to use only vaccines made by Pfizer and Moderna, which use a different technology and have not been connected to blood clots. Denmark plans to open vaccinations to all people older than 16 in late June and to finish vaccinating them by early August.

Two people in Denmark have died of blood clots that authorities think may have been connected to the AstraZeneca vaccine. In Britain and Germany, authorities have identified about 30 cases of blood clots each among the millions of doses administered.

British authorities credit the Oxford-designed AstraZeneca vaccine with helping them beat back a tremendous surge in coronavirus cases in January. They say the rollout has been safe. But they also started recommending the use of alternative vaccines for people younger than 30 last week because of the clotting concerns.

The Danish decision was another blow to a vaccine that has been a key part of global strategies to conduct vaccinations quickly, and there are plans to roll it out in 140 countries as part of Covax, a program designed to give lower-income nations access to inoculations. The AstraZeneca vaccine is far cheaper than many of its competitors — about $4 a dose, compared with rivals that can cost four or five times as much — and it is easier to store and transport. AstraZeneca billed it as “a vaccine for the world.” But there has been rising hesitancy in Europe about it. The United States and Switzerland have not yet approved the vaccine for use.

Danish authorities said people who have had one dose of the AstraZeneca vaccine and were awaiting their second dose will be offered Pfizer or Moderna shots instead.

Not all countries have been so cautious about the AstraZeneca vaccine: After the Danish announcement, Czech Interior Minister Jan Hamacek said he had asked the Czech ambassador in Copenhagen to try to buy Denmark’s unused AstraZeneca doses.

“We are looking for vaccines all over the world,” Hamacek wrote on Twitter.

Denmark has about 52,000 doses of the AstraZeneca vaccine in stock that it will not use, according to data from the European Center for Disease Prevention and Control. It has contracted for more doses under a joint European Union vaccine purchasing program.

European policymakers were frustrated with AstraZeneca even before the clotting issues because the company had delivered only a third of the doses it had agreed to produce for Europe in the first quarter of the year, dealing a major blow to E.U. vaccination efforts. Vaccines from other manufacturers appear to be playing an increasingly larger role in the E.U. vaccine strategy. European Commission President Ursula von der Leyen on Wednesday announced a new order of vaccines from Pfizer, which has had far fewer delivery problems and agreed to accelerate deliveries of current orders in the coming months.