Italy’s suspension of another batch was tied to a man in Sicily who died after receiving his shot. It is unclear whether a blood clot was involved.

The vaccine manufactured by AstraZeneca has been injected into more than 142,000 people in Denmark, which has a population of around six million.

The Danish Health Minister Magnus Heunicke said on Twitter that it was “currently not possible to determine whether there is a connection”. He added: “We acted early, it needs a thorough investigation.”

Denmark had already cut the target for the completion of its vaccination campaign, partly due to delivery delays. The safety break will delay it further.

AstraZeneca’s vaccine was screened for potential safety issues over the past year while being tested in clinical trials. Two vaccinated volunteers in the UK developed neurological symptoms related to transverse myelitis, an inflammatory syndrome that affects the spinal cord and is often caused by viral infections.

These concerns temporarily put the vaccine to a halt around the world, but the investigation ultimately found no evidence to link the symptoms to the vaccine. One of the sick participants was later found to have an undiagnosed case of multiple sclerosis.

Since then, more than 70 countries have approved the vaccine, with the exception of the United States, where regulators are waiting for data from a large clinical trial expected in the next few weeks. A Food and Drug Administration decision to approve AstraZeneca’s vaccine is likely more than a month away.

The largest real world data on the safety of the vaccine comes from the UK, which had given 9.7 million doses in the last month. The UK Medicines Agency, the regulator of medicines and health products, said: “The number and types of suspected adverse reactions reported to date are not uncommon when compared to other types of vaccines routinely used.”

Rebecca Robbins reported from Bellingham, Washington, and Thomas Erdbrink from Amsterdam. Jason Horowitz and Emma Bubola reported from Italy, Benjamin Mueller from London and Denise Grady from New York.