Finland has become the latest Scandinavian country to suspend the AstraZeneca vaccine - despite the European Medicines Agency (EMA) concluding it was "safe and effective".
The country's public health authority said two people developed blood clots after being vaccinated. As a result, jabs will be suspended "until there is more information and a possible causality can be assessed".
Dozens of European countries had suspended the vaccine amid reports of blood clots.
Some, such as Italy, Germany and Spain indicated they would restart AstraZeneca vaccinations after the EMA's safety review on Thursday.
But Norway, Sweden and Denmark said they would not be lifting their suspensions.
All three countries said they were reviewing the EMA verdict that the vaccine's benefits outweigh its risks following 25 reports of rare but serious blood clots in Europe.
France's health authority said on Friday that vaccinations could restart, but only in people over the age of 55, citing serious cases of rare blood clots in young people who received the AstraZeneca vaccine as the reason why.
Norway, Sweden and Denmark continue pause on vaccination
Geir Bukholm, the director of the Division of Infection Control at the Norwegian Institute for Public Health, said the vaccination pause would continue in Norway.
"Due to the several serious cases in Norway, we want to thoroughly review the situation before we make a conclusion," he said. "This will take some time, and we will provide an update at the end of next week."
Sweden's public health agency said their national regulator was investigating cases of blood clots in the country.
"[We] hope that next week we will be able to decide how best to use this vaccine in the future," said Swedish epidemiologist Anders Tegnell.
In Denmark, the health authority said that there were "observed cases of severe but rare blood clots after vaccination with the COVID-19 vaccine from AstraZeneca" and they would continue to pause vaccinations as they review EMA's assessment.
Professor Neil Mabbott, chair of immunopathology at the University of Edinburgh, said decisions to stop the AstraZeneca vaccine were "overcautious" as it is proven to stop death and hospitalisation and was given the green light by the EU and UK regulators.
"When you are giving out millions of vaccines in a short period of time, which has been the case...it’s not surprising that you might expect to see rare or apparent associations at least of these kind of events," he explained, stating that the blood clotting events remained "extremely rare".
"The COVID-19 infection itself can in some individuals cause clotting so having the vaccine itself actually protects you from having these events," Mabbott added.
Investigations ongoing about reported blood clots
On Thursday, a Norwegian medical team claimed there was a link between the AstraZeneca vaccine and blood clots.
"We have obtained results which may explain the clinical course of our hospitalised patients," said Pål André Holme, a professor of haematology at Oslo University Hospital, a few hours before the EMA briefing.
"These patients had a powerful immune response which led to the formation of antibodies which can affect the platelets and thus lead to a blood clot," he said, stating that he did not see any other possibility but that it was linked to the vaccine.
Norway, where some 120,000 people received a first dose of the AstraZeneca vaccine, has had six cases of serious side effects, two of which were fatal.
There were a total of 25 reported cases of rare blood clots in people vaccinated in the EU, according to EMA, of which nine people died, according to France's health authority.
"Almost all of these cases occurred in people under the age of 55, and in a majority of women," the French health authority's opinion said.
There have been three reported cases in France including a 26-year-old who developed disseminated intravascular coagulation (blood clots throughout the body) and a 51-year-old man and a 24-year-old woman who had low platelets in the blood, which are necessary to help the blood clot.
Some of the first reported cases were in Austria where a 49-year-old woman died of multiple blood clots and a 35-year-old woman was hospitalised with a pulmonary embolism.
The UK's regulator said there were five such reports in the country but that "this has been reported in less than 1 in a million people vaccinated so far in the UK, and can also occur naturally – a causal association with the vaccine has not been established."
EMA adds warning about blood clots to vaccine but concludes is 'safe and effective'
The European regulator had determined on Thursday that the benefits of the vaccine, which has been shown to prevent death and hospitalisation due to COVID-19, outweigh the possible risks.
EMA executive director Emer Cooke qualified, however, that the regulator "cannot rule out definitively a link between these [blood clot] cases and the vaccine," saying the safety review committee would continue its investigations.
Officials suggested adding a warning about rare blood clots to the AstraZeneca vaccine.
"We have to continually remind ourselves what a difficult situation we're in. This pandemic is costing lives. We have vaccines that are safe and effective that can help prevent death and hospitalisation. We need to use those vaccines within the environments that we have them," Cooke said to explain why the benefits outweigh the risks.
The EMA committee "has concluded that there is no increase in the overall risk of blood clots with this vaccine," said Dr Sabine Straus, chair of the EMA safety review committee, adding that there was no evidence of a batch issue.
However, she said, there were a few cases where "tiny clots developed in multiple blood vessels in the first 7-14 days after vaccination," Straus said. There were also a few cases of clots in blood vessels draining blood from the brain, she added.
Halting vaccinations 'will lead to deaths' — drug safety expert
The opinion of the EMA was hotly anticipated at a time when the European Union, in the midst of a vaccine shortage, is counting on millions of doses of this vaccine developed by British-Swedish firm AstraZeneca.
The World Health Organization has also said there is no evidence the vaccine is to blame.
Some expert had criticised the decision by countries to suspend use of the AstraZeneca vaccine.
"The downside of this [suspending the AstraZeneca shot] is that we will drive up vaccine hesitancy and thus decrease the amount of the population that will be finally vaccinated (…). Just even the pause in vaccination will lead to deaths," said Anthony Cox, a reader in clinical pharmacy and drug safety at the University of Birmingham.
Following the EMA's announcement, Italy said it would restart its rollout of AstraZeneca vaccinations on Friday. France, Germany and Spain also announced similar moves though France will restrict the vaccine to people over the age of 55.
French government officials said Prime Minister Jean Castex would get the vaccine on Friday afternoon to show government confidence in the jab.
This story has been updated with the announcement from Finland and from France. Expert comments have also been added.