Norway has extended a suspension of the AstraZeneca vaccine for three weeks.
The Norwegian Institute of Public Health said the temporary pause would continue until April 15 because “further investigations are necessary”.
Earlier this month, Norway and several other European countries halted the rollout of AstraZeneca vaccines following reports of blood clotting.
Last week, the European Medicines Agency (EMA) reaffirmed that the jab was “safe and effective”, prompting several nations to resume vaccination programmes.
The World Health Organization (WHO) has also stated that the benefits of AstraZeneca’s vaccine outweigh the risk of side effects.
But in a statement on Friday, Norway confirmed that the suspension would remain in place until more information was available.
“It is a difficult but correct decision to extend the pause for the AstraZeneca vaccine,” said Geir Bukholm, Director of Infection Control and Environmental Health at the Institute.
“We believe it is necessary to carry out more investigations into these cases so we can give the best possible advice about vaccination to the population in Norway.”
Norway initially suspended AstraZeneca vaccines on March 11, and say they have received reports of four deaths in the country linked to thrombosis.
“All patients in Norway and Europe with the severe clinical picture of blood clots, haemorrhages and low platelet counts developed symptoms within a period of about two weeks after vaccination,” the institute said.
On Thursday, Denmark also extended its suspension of AstraZeneca vaccines for three weeks, noting that the EMA said severe cases of rare side effects cannot be excluded.
Norwegian authorities have acknowledged that delaying the resumption has a “direct effect” on easing anti-virus restrictions.
“The AstraZeneca vaccine is a good vaccine that protects risk groups against COVID-19,” said Bukholm.
“However, it is important to weigh the benefits of vaccination against the risk of rare but serious side effects from continued use of the AstraZeneca vaccine. We need more time to find out more about this balance.”
The Norwegian Institute of Public Health says they are working with clinical experts both in Norway and abroad to identify whether there is any connection between the vaccine and blood clotting and will inform the EMA of any findings.
Around 200,000 doses of AstraZeneca in Norway remain in storage, while the immunisation programme is delayed by up to two weeks, they added.
Sweden, Iceland, and Finland announced this week that they will resume the use of AstraZeneca’s vaccine, but reserve it for the elderly population for the time being.
