LONDON — Ireland and the Netherlands have joined the growing list of countries that have suspended the use of the coronavirus vaccine developed by AstraZeneca and the University of Oxford over blood clot concerns.

The Dutch government said on Sunday that the Oxford-AstraZeneca vaccine would not be used until at least March 29, while Ireland said earlier in the day that it had temporarily suspended the shot as a precautionary step.

The World Health Organization has sought to downplay ongoing safety concerns, saying last week that there is no link between the shot and an increased risk of developing blood clots. The United Nations health agency has urged countries to continue using the Oxford-AstraZeneca vaccine.

Despite this, a number of European countries have already paused the use of the Oxford-AstraZeneca vaccine. It has added to the woes of the region’s ailing vaccination campaign at a time when Germany’s public health agency has warned that a third wave of coronavirus infections has already begun.

Thailand has also halted its planned deployment of the vaccine.

The move to pause its use by Dutch and Irish officials came shortly after Norway’s medicines agency said it had been notified of three health workers being treated in hospital for bleeding, blood clots and a low count of blood platelets after receiving the Oxford-AstraZeneca vaccine. Norway has put its Oxford-AstraZeneca vaccine program on hold.

Geir Bukholm, director of the Division of Infection Control and Environmental Health at the Norwegian Institute of Public Health, said Norway’s medicines agency would “follow up on these suspected side effects and take the necessary measures in this serious situation.”

Europe’s drug regulator, the European Medicines Agency, has also said there is no indication that the Oxford-AstraZeneca vaccine is causing blood clots, adding that it believes the vaccine’s benefits “continue to outweigh its risks.”

The EMA acknowledged some European countries had paused the use of the Oxford-AstraZeneca shot but said inoculations may continue to be administered while an investigation of blood clot cases is ongoing.

“A careful review of all available safety data of more than 17 million people vaccinated in the European Union (EU) and UK with COVID-19 Vaccine AstraZeneca has shown no evidence of an increased risk of pulmonary embolism, deep vein thrombosis (DVT) or thrombocytopenia, in any defined age group, gender, batch or in any particular country,” AstraZeneca said in a statement on Sunday.

The most common side effects of the Oxford-AstraZeneca vaccine, which does not contain the virus and cannot cause Covid, are typically mild or moderate and improve within a few days of vaccination.

The pharmaceutical giant said that across the EU and U.K. there had been 15 events of deep vein thrombosis and 22 events of pulmonary embolism reported among those vaccinated.

“This is much lower than would be expected to occur naturally in a general population of this size and is similar across other licensed COVID-19 vaccines,” AstraZeneca said.

“Covid definitely causes coagulation disorders and each of the vaccines prevents Covid disease, including more severe cases,” said Stephen Evans, professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine.

“Therefore, it is extremely likely that the benefit of the vaccine notably outweighs any risk for coagulation disorders and the vaccine prevents other consequences of Covid including deaths from other causes.”

Evans said it was “entirely reasonable” to conduct studies into the vaccines and coagulation disorders, but added: “It seems a step too far in taking precautions that would stop people getting vaccines that would prevent disease.”

Many high-income countries — such as the U.K., France, Australia and Canada — have chosen to continue with their respective rollout of the Oxford-AstraZeneca vaccine.

“If clear evidence of serious or life-threatening side-effects emerges that will have important consequences,” Adam Finn, professor of pediatrics at the University of Bristol, said in a statement.

“However so far it hasn’t and it’s highly undesirable to disrupt a complex and urgent programme every time people develop illnesses after receiving vaccine that may be coincidental and not causally related. Making the right call in situations like this is not easy but having a steady hand on the tiller is probably what is needed most,” Finn said.