The suspension of Italy from another group has been linked to a man in Sicily who died after receiving his shot. It is unclear if there was a blood clot involved.
In Denmark, with a population of about six million, more than 142,000 people were injected with the vaccine manufactured by AstraZeneca.
The Danish Minister of Health, Magnus Heunicke, said on Twitter that it is “currently not possible to conclude whether there is a connection.” He added: “We acted early, it needs to be thoroughly investigated.”
Denmark has already scaled down the target for finishing the vaccination campaign in part due to delays in deliveries. The safety break will further delay it.
The AstraZeneca vaccine was scrutinized last year over possible safety issues while being tested in clinical trials. Two vaccinated volunteers in Britain have developed neurological symptoms similar to transverse myelitis, an inflammatory syndrome that affects the spinal cord and is often caused by viral infections.
These concerns temporarily halted worldwide trials with the vaccine, but investigations eventually found no evidence linking the symptoms to the vaccine. It was later found that one of the participants who became ill had an undiagnosed case of multiple sclerosis.
More than 70 countries have meanwhile approved the vaccine, with the notable exception of the United States, where regulators are awaiting data from a major clinical trial expected in the next few weeks. A decision approved by the Food and Drug Administration or AstraZeneca’s vaccine is likely to be more than a month away.
The extensive real data on the safety of the vaccine comes from Britain, which administered 9.7 million doses last month. The UK’s drug regulator, the Medicines and Healthcare Products Regulatory Agency, said: “The number and nature of suspected side effects reported so far are not uncommon compared to other types of vaccines used frequently.”
Rebecca Robbins reported from Bellingham, Wash., and Thomas Erdbrink of Amsterdam. Jason Horowitz and Emma Bubola contribution made from Italy, Benjamin Mueller of London and Denise Grady of New York.