Here we take a look at the key questions surrounding the situation.
There have been a small number of reports of people experiencing blood clots in the days and weeks after their vaccination.
The European Medicines Agency (EMA) reported one person in Austria was diagnosed with blood clots and died 10 days after vaccination, but it stressed there is “currently no indication that vaccination has caused these conditions”.
Another person was admitted to hospital in Austria with pulmonary embolism (blockage in arteries in the lungs) after being vaccinated, while one death involving a blood clot was reported in Denmark.
A 50-year-old man is also thought to have died in Italy from deep vein thrombosis (DVT), while there has been an unconfirmed report of another death in Italy.
Ireland’s decision followed reports of serious clotting in adults in Norway which left four people in hospital.
– Which countries are involved?
Ireland and the Netherlands on Sunday joined a list that already included Denmark, Norway and Iceland, which said they are temporarily halting all AstraZeneca vaccinations to investigate further.
The Netherlands said it is suspending its AstraZeneca rollout as a precaution for two weeks after a small number of new reports in Denmark and Norway of blood clotting and lowered levels of blood platelets in people aged under 50.
Bulgaria’s prime minister said its suspension would last until the EMA issued a written statement that the vaccine is safe.
Italy also followed Austria, Estonia, Latvia, Luxembourg and Lithuania in banning jabs from one particular batch of one million AstraZeneca vaccines, which was sent to 17 countries, after reports of a death.
Very few details have been given about the individuals, including whether they had any underlying conditions that already raised the risk of blood clots.
Thailand and Congo said they would delay use of the AstraZeneca vaccine.
– What has Ireland said?
On Sunday, Minister for Health Stephen Donnelly said: “The decision to temporarily suspend use of the AstraZeneca Covid-19 vaccine was based on new information from Norway that emerged late last night.
“This is a precautionary step.”
– And what about Northern Ireland?
Health Minister Robin Swann asked for an update from the UK’s regulator – the Medicines and Healthcare products Regulatory Agency (MHRA) – following the Republic’s decision, the department of health in Northern Ireland said.
The rollout there is to continue “in line with MHRA guidance”, the department added.
– What do the European and UK medicines regulators say?The MHRA had already issued a statement last week saying more than 11 million doses of the AstraZeneca vaccine had been administered across the UK with no issues.
After the Republic of Ireland’s decision to suspend use, Dr Phil Bryan, MHRA vaccines safety lead said: “We are aware of the action in Ireland.
“We are closely reviewing reports but given the large number of doses administered, and the frequency at which blood clots can occur naturally, the evidence available does not suggest the vaccine is the cause.”
He said people “should still go and get their Covid-19 vaccine when asked to do so.”
The EMA said in a statement on Thursday that the vaccine’s benefits continue to outweigh its risks and that jabs can continue to be administered while it carries out a review into any incidents of blood clots.
It said that as of March 10 there were just 30 reports of blood clots among almost five million people given the vaccine across Europe.
– What about the World Health Organisation (WHO)?
Director general Tedros Adhanom Ghebreyesus said WHO is continuing to keep a close eye on the safety of the vaccines but said it was important to note the EMA “has said there is no indication of a link between the vaccine and blood clots and that the vaccine can continue to be used while its investigation is ongoing”.
His comments echoed remarks made by WHO spokeswoman Dr Margaret Harris, who described the vaccine as “excellent”.
– Are UK scientists worried?
No. The overwhelming scientific opinion is that there is no certain link between blood clots and the vaccine, and the reported cases could easily be coincidental.
They argue the risks from Covid-19 far outweigh any potential side-effects from the jab, with many saying blood clots are fairly common, regardless of vaccination.
Stephen Evans, professor of pharmacoepidemiology at the London School of Hygiene & Tropical Medicine, said: “The problem with spontaneous reports of suspected adverse reactions to a vaccine are the enormous difficulty of distinguishing a causal effect from a coincidence.
“This is especially true when we know that Covid-19 disease is very strongly associated with blood clotting and there have been hundreds if not many thousands of deaths caused by blood clotting as a result of Covid-19 disease.
“The first thing to do is to be absolutely certain that the clots did not have some other cause, including Covid-19.”
– What has AstraZeneca said?The pharmaceutical giant said a “careful review of all available safety data” of more than 17 million people vaccinated in the EU and UK with the AstraZeneca jab has shown “no evidence of an increased risk of pulmonary embolism, deep vein thrombosis (DVT) or thrombocytopenia, in any defined age group, gender, batch or in any particular country.”
Its chief medical officer Dr Ann Taylor said the number of cases of blood clots reported in this group “is lower than the hundreds of cases that would be expected among the general population”.