A cascading number of European countries — including Germany, France, Italy and Spain — suspended use of AstraZeneca’s COVID-19 vaccine Monday over reports of dangerous blood clots in some recipients, though the company and international regulators say there is no evidence the shot is to blame.

AstraZeneca’s formula is one of three vaccines in use on the continent. But the escalating concern is another setback for the European Union’s vaccination drive, which has been plagued by shortages and other hurdles and is lagging well behind the campaigns in Britain and the U.S.

The EU’s drug regulatory agency called a meeting for Thursday to review experts’ findings on the AstraZeneca shot and decide whether action needs to be taken.

The furor comes as much of Europe is tightening restrictions on schools and businesses amid surging cases of COVID-19.

Germany’s health minister said the decision to suspend AstraZeneca shots was taken on the advice of the country’s vaccine regulator, the Paul Ehrlich Institute, which called for further investigation into seven cases of clots in the brains of people who had been vaccinated.

“Today’s decision is a purely precautionary measure,” Jens Spahn said.

French President Emmanuel Macron said his country will likewise stop dispensing the vaccine until at least Tuesday afternoon. Italy also announced a temporary ban, as did Spain, Portugal and Slovenia.

Other countries that have done so over the past few days include Denmark, which was the first, as well as Ireland, Thailand, the Netherlands, Norway, Iceland, Congo and Bulgaria. Canada and Britain are standing by the vaccine for now.

In the coming weeks, AstraZeneca is expected to apply for U.S. authorization of its vaccine. The U.S. now relies on Pfizer’s, Moderna’s and Johnson & Johnson’s shots.

AstraZeneca said there have been 37 reports of blood clots out of more than 17 million people vaccinated in the 27-country EU and Britain. The drugmaker said there is no evidence the vaccine carries an increased risk of clots.

In fact, it said the incidence of clots is much lower than would be expected to occur naturally in a general population of this size and is similar to that of other licensed COVID-19 vaccines.

The World Health Organization and the EU’s European Medicines Agency have also said that the data does not suggest the vaccine caused the clots and that people should continue to be immunized.

“Many thousands of people develop blood clots annually in the EU for different reasons,” the European Medicines Agency said. The incidence in vaccinated people “seems not to be higher than that seen in the general population.”

The agency said that while the investigation is going on, “the benefits of the AstraZeneca vaccine in preventing COVID-19, with its associated risk of hospitalization and death, outweigh the risks of side effects.”

Blood clots can travel through the body and cause heart attacks, strokes and deadly blockages in the lungs. AstraZeneca reported 15 cases of deep vein thrombosis, or a type of clot that often develops in the legs, and 22 instances of pulmonary embolisms, or clots in the lungs.

The AstraZeneca shot has become a key tool in European countries’ efforts to boost their sluggish vaccine rollouts. It is also pillar of a U.N.-backed project known as COVAX that aims to supply COVID-19 vaccines to poorer countries. That program continues unaffected by the European suspension.

Pfizer’s and Moderna’s vaccines are also used on the European continent, and J&J’s one-shot vaccine has been authorized but not yet delivered.

Dr. Michael Head, a senior research fellow in global health at the University of Southampton in England, said there is no data yet to justify suspending the AstraZeneca vaccine and called the decision “baffling.”

“Halting a vaccine rollout during a pandemic has consequences,” Head said. “This results in delays in protecting people, and the potential for increased vaccine hesitancy, as a result of people who have seen the headlines and understandably become concerned.”

Spahn, the German health minister, defended the country’s decision, saying, “The most important thing for confidence is transparency.” He said both first and second doses would be suspended.

Germany has received slightly over 3 million doses of the AstraZeneca vaccine, and about half of those have so far been administered, compared with almost 7 million of the Pfizer shot and about 285,000 from Moderna.

German authorities have encouraged anyone who feels increasingly ill more than four days after receiving the shot — for example, with persistent headaches or dot-shaped bruises — to seek medical attention.

The head of the Spanish Medicines Agency, Maria Jesús Lamas, said Spain detected its first case of clots on Saturday. She said the ban was “not an easy decision” because it further slows the nation’s vaccination campaign, but it was the “most prudent” approach.

Almost 940,000 people in Spain have received the AstraZeneca shot.

Some European countries, meanwhile, have begun reimposing restrictions in a bid to beat back a resurgence in infections, many of them from variants of the original virus.

In Italy, 80% of children nationwide couldn’t attend classes after stricter rules in more regions took effect on Monday. In Poland, bolstered restrictions were applied to two more regions, including Warsaw. Paris could go into lockdown in a matter of days because intensive care units are getting swamped with COVID-19 patients.

And calls are growing in Germany to “ pull the emergency brake” in regions where cases are rising.