A man waits to get vaccinated with the Astrazeneca COVID19 vaccine in a vaccination center of Saint-Jean-de-Luz, southwestern France, Thursday, April 8, 2021. (AP Photo/Bob Edme)

THE HAGUE, Netherlands — In Spain, residents now have to be over 60 to get an AstraZeneca coronavirus vaccine. In Belgium, over 55. In the United Kingdom, authorities recommend the shot not be given to adults under 30 where possible, and Australia’s government announced similar limits Thursday to AstraZeneca shots for those under 50.

A patchwork of advice was emerging from governments across Europe and farther afield, a day after the European Union’s drug regulator said there was a “possible link” between the AstraZeneca vaccine and a rare clotting disorder while reiterating the vaccine is safe and effective.

Regulators in the United Kingdom and the EU both stressed that the benefits of receiving the vaccine continue to outweigh the risks for most people, and the EU agency maintained its guidance that the vaccine can be used in all adults. But experts fear the confusing messages about the vaccine could still dampen enthusiasm for it at a time when Europe and many other parts of the world are facing surging cases.

Experts hammered home the rarity of the clots Thursday.

“The risks appear to be extremely low from this very rare side effect,” Anthony R. Cox, of the University of Birmingham’s School of Pharmacy, told the BBC. “I mean it’s the equivalent of the risk of dying in the bath, drowning in the bath, for example, it’s that rare, or a plane landing on your house.”

Dr. Sabine Straus, chair of the EU regulator’s Safety Committee, said the best data was from Germany, where there was one report of the clots for every 100,000 doses given, although she noted far fewer reports in the U.K. Still, that’s less than the clot risk that healthy women face from birth control pills, noted another expert, Dr. Peter Arlett. The agency said most of the cases reported were in women under 60 within two weeks of vaccination, though it was unable to identify specific risk factors based on current information.

The EU is trying, but so far failing, to avoid different policies among its 27 nations, which all look to the European Medicines Agency for guidance. Health Commissioner Stella Kyriakides called Wednesday evening for a coherent approach to ensure that “on the basis of the same set of evidence, similar decisions are taken in different member states.”

News of the tiny risk already is already having an effect. In Croatia, the government said that one in four people due to get an AstraZeneca shot Thursday didn’t show up. Poland, too, has also seen people cancel or not appear for appointments to get the vaccine.

French general practitioner Dr. Joel Valendoff said many of his patients were still coming to get their shot, but many others were canceling.

When vaccines first became available, “I was refusing people because I had a lot of demand and not enough vaccines. Today I am facing the opposite. I have vaccines but not enough volunteers.”

Mbaye Thiam, a 59-year-old Parisian, was among those who got vaccinated.

“I am closely monitoring the COVID-19 situation throughout the world. I am not worried. In an exceptional situation we need exceptional measures,” he said. “It is true that the vaccine was created in a record time, but the world has stopped and we need solutions to make it start again, and the vaccine is one of the solutions.”

European Commission spokesman Stefan De Keersmaecker said the EMA’s findings were based on its stringent monitoring system and that should promote trust among the bloc’s 27 member states.

“We want to avoid, of course, a vaccination hesitancy,” he said.

Any such reluctance is worrying since experts say the shots are key to stamping out the coronavirus pandemic, but AstraZeneca’s role is especially vital. The vaccine, which is cheaper and easier to store than many others, is critical to immunization campaigns in Europe and the U.K. and is also a pillar of the U.N.-backed program known as COVAX that aims to get vaccines to some of the world’s poorest countries.