Denmark, Norway and Iceland have temporarily suspended the use of AstraZeneca's Covid-19 vaccine over concerns about patients developing post-jab blood clots, as the manufacturer and the European Medicines Agency insisted the vaccine was safe.
The EMA said that information available so far indicated the risk of blood clots in those vaccinated against the coronavirus was "no higher than that seen in the general population."
It also said that European countries could keep using the AstraZeneca vaccine while the issue was investigated, concluding that "the vaccine's benefits continue to outweigh its risks".
Denmark, the first to announce it was suspending the jab, stressed that the move was precautionary.
"It has not been determined, at the time being, that there is a link between the vaccine and the blood clots," the country's health authority said.
As of 9 March, 22 cases of blood clots had been reported among more than three million people vaccinated in the European Economic Area, the EMA said.
Austria announced on Monday that it had suspended the use of a batch of AstraZeneca vaccines after a 49-year-old nurse died of "severe blood coagulation problems" days after receiving an anti-Covid shot.
Five other European countries - Estonia, Latvia, Lithuania, Luxemburg and Italy - have also suspended the use of vaccines from this batch, which was sent to 17 European countries and consisted of one million jabs.
Yesterday, the EMA said a preliminary probe showed that the batch of AstraZeneca vaccines used in Austria was likely not to blame for the nurse's death.
Denmark however suspended the use of its entire AstraZeneca supply, as did Iceland and Norway in subsequent announcements today citing similar concerns.
AstraZeneca, an Anglo-Swedish company which developed the vaccine with Oxford University, defended the safety of its product.
In a statement to RTÉ a spokesperson said: "Patient safety is the highest priority for AstraZeneca. Regulators have clear and stringent efficacy and safety standards for the approval of any new medicine, and that includes Covid-19 Vaccine AstraZeneca. The safety of the vaccine has been extensively studied in phase III clinical trials and peer-reviewed data confirms the vaccine is generally well tolerated."
The UK, whose widely-praised vaccine rollout has been largely underpinned by the AstraZeneca jab, also defended it as "both safe and effective", while Sweden and the Netherlands said they would continue to use it.
The UK's Medicines and Healthcare Products Regulatory Agency said that links between AstraZeneca's vaccine and blood clots have not been confirmed and encouraged people to continue taking the vaccine.
"This is a precautionary measure by the Danish authorities. It has not been confirmed that the report of a blood clot was caused by the AstraZeneca Covid-19 Vaccine. People should still go and get their Covid-19 vaccine when asked to do so," it said in a statement.
British Prime Minister Boris Johnson's spokesman said: "We've been clear that it's both safe and effective ... and when people are asked to come forward and take it, they should do so in confidence."
Earlier this week, the Health Products Regulatory Authority in Ireland said it is closely monitoring the Austrian investigation.
The HPRA said that at present there is "no evidence of a causal relationship" between the vaccine and the events and the suspension of a specific batch is a "precautionary action by the Austrian regulator pending further investigation".
The Danish suspension, which will be reviewed after two weeks, is expected to slow down the country's vaccination campaign.
If Denmark were to move on without AstraZeneca, its health authority said it expected to have its entire adult population vaccinated by mid-August instead of early July.
"We are of course saddened by this news," said Prime Minister Mette Frederiksen.
Ms Frederiksen, who has pushed for the production of more vaccines and has formed a controversial alliance with Austria and Israel to do so, defended the Danish health authorities' decision.
"Things have gone well in Denmark, but there are some risks linked to the AstraZeneca vaccine that need to be examined more closely," she told reporters. "That seems to me to be the right way to proceed."
Health Authority director Soren Brostrom stressed that Denmark was pausing use of the AstraZeneca jab, not terminating it.
"But both we and the Danish Medicines Agency must act on information about possible serious side effects, both in Denmark and in other European countries," Dr Brostrom said.
The EMA has launched an investigation into the death of one person who died after receiving the vaccine in Denmark.
Around 25% of those who have received a first dose in Denmark, a country of 5.8 million, were given the AstraZeneca jab.
In total, 3.8% of the population have received two vaccine doses and 13.4% at least one dose.
Pfizer vaccine 97% effective against symptomatic Covid-19 - study
Pfizer/BioNTech's coronavirus vaccine offers more protection than earlier thought with effectiveness in preventing symptomatic disease reaching 97%, according to real-world evidence published by the pharmaceutical companies.
Using data from 17 January to 6 March from Israel's national vaccination campaign, Pfizer/BioNTech found that prevention against asymptomatic disease also reached 94%.
An earlier real-world study using data from between 20 December 2020 and 1 February 2021 had showed effectiveness at preventing symptomatic disease at 94% and asymptomatic illness at 92%.
"This comprehensive real-world evidence ... can be of importance to countries around the world as they advance their own vaccination campaigns one year after the World Health Organization declared Covid-19 a pandemic," the two pharmaceutical companies said in a statement.
Israel's inoculation campaign is the fastest in the world, with about 40% of the population already fully vaccinated against the virus.
Israel, which launched its vaccination campaign in December, has given the recommended two jabs of the Pfizer/BioNTech vaccine to just under four million of its roughly nine million people.
More than five million have received one shot.
"Incidence rates in the fully vaccinated population have massively dropped compared to the unvaccinated population, showing a marked decline in hospitalised cases due to COVID-19," said Israel's Ministry of Health director Yeheskel Levy.