Q&A: How serious are the AstraZeneca vaccine safety concerns?

Temporary suspension of jab in Ireland follows similar move in Norway, Denmark and Iceland

The AstraZeneca vaccine is one of four authorised for use against Covid-19 but the State has temporarily suspended its administration due to possible health concerns about it.

What is the AstraZeneca vaccine?

The Oxford-AstraZeneca vaccine, as it also known, is one of four vaccines authorised for use against Covid-19 in the State. The others are produced by Pfizer, Moderna and Johnson & Johnson or Janssen, whose jab was just authorised by the European Medicines Agency last week.

How does the AstraZeneca jab work?


The vaccine works differently from the Pfizer and Moderna mRNA vaccines, which inject part of the coronavirus’s genetic code into the body to provoke an immune response. The AstraZeneca jab is made from a weakened version of a common cold virus that has been changed to look like a coronavirus.

It does not cause illness, but once injected, it teaches the body’s immune system how to fight the coronavirus if infected. A single shot of the vaccine has been found to be highly protective, reducing the chances of severe illness and hospitalisation by more than 80 per cent.

Why is it in the news now?

The State's deputy chief medical officer Dr Ronan Glynn said in a statement on Sunday morning that following new information received from the Norwegian Medicines Agency on Saturday evening - and following discussions with the Health Products Regulatory Authority (HPRA), the State's medicines watchdog - the National Immunisation Advisory Committee (NIAC) has recommended that the administration of the AstraZeneca vaccine should be temporarily deferred.

Why has this decision been made?

A report from the Norwegian Medicines Agency (EMA) detailed four new reports of serious blood clotting in adults after being vaccinated with AstraZeneca. Dr Glynn stressed that it has not been concluded that there is any link between the vaccine and these cases but that, as a precaution and pending further information, the NIAC has recommended the temporarily deferral of the jab.

How serious are the safety concerns about the vaccine?

Prof Karina Butler, chair of NIAC, said on Sunday that NIAC was “absolutely delighted” with the ”proven effect” of the AstraZeneca vaccine and its benefits at preventing serious effects from Covid-19.

She said that a "safety signal" was raised in Norway about "four serious, very rare, very serious clotting events" that would not normally be expected, but she noted that "clotting problems happen to people irrespective of whether they get the vaccine". She hoped that these reports were just an overreaction and that a decision would be made concerning the safety of the vaccine within the week.

Further information is expected from the EMA in the next few days, including a review of the cases in Norway.

In a statement at lunchtime, NIAC said that “to date, no reports of similar events to those in Norway had been received by the HPRA. Over 117,000 doses of the AstraZeneca Covid-19 vaccine had been given in the Republic to date, it noted.

Dr Glynn told RTÉ Radio on Sunday that there was no evidence that the AstraZeneca had caused the “unusual cluster” in Norway where there was “very serious” and “very rare” blood clotting in the brains of people in their 30s and 40. However, the rollout of this vaccine was being paused as a precaution, particularly because it was due to be given to people aged between 16 and 69 with serious underlying health conditions and who were at risk of very severe disease from Covid-19.

What exactly happened in Norway?

Norway reported on Saturday that a further three healthcare workers, all under the age of 50, who received the AstraZeneca vaccine were being treated in hospital for bleeding, blot clots and a low count of blood platelets.

The Norwegian Medicines Agency said that similar incidents had been reported in other countries. Norway halted the rollout of that vaccine on Thursday, leading Denmark and Iceland to follow suit. The European Medicines Agency is investigating.

The World Health Organisation has said there is no causal link between the vaccine and the blood clotting. At least 10 countries have now suspended the use of the AstraZeneca vaccine.

What happens now?

Dr Glynn said NIAC was discussing the matter further on Sunday. Minister for Health Stephen Donnelly said the temporary suspension was a "precautionary step" and that the Government would provide an update after NIAC's meeting.

What should people do who have received the AstraZeneca vaccine?

Dr Glynn said that it was not unusual for people to feel tired, muscle pain or fever after they receive Covid-19 vaccines. He advised people that if they feel unwell more than three days after receiving their AstraZeneca doses or if they notice blue spots on their skin, they should consult their doctors.

The Department of Health said that these are rare events that usually occur within 14 days of the vaccine. The HPRA has urged doctors and the public to report any side effects to Covid-19 vaccines to it.

What happens to people who were due to receive the AstraZeneca vaccine?

HSE chief clinical officer Colm Henry said that healthcare workers and people with underlying health conditions who were due to receive the jab would have their vaccinations suspended. Vaccinations of people over 70 would continue with the Pfizer and Moderna vaccines.

If the AstraZeneca jab cannot be given, what does this mean for the State’s vaccine rollout?

It would slow down the rollout even more. There have already been repeated delays and interruptions to the promised delivery schedule from AstraZeneca. Up to the end of the first week of March, about a fifth of all vaccine doses delivered to the State - 122,400 out of 613,650 - were AstraZeneca vaccines.

The Government had estimated that they would make up 21 per cent of the vaccines being administered between April and June so it would be a major setback for the Government if these vaccines could not be used. It would make the State even more reliant on the other three authorised vaccines - or other vaccines being authorised in the EU in the weeks and months ahead. This would heap further pressure on the Government to find alternative supplies.

How many vaccines had AstraZeneca promised?

The British-Swedish drugmaker had promised the EU 90 million doses by the end of March but reduced that to 40 million last month due to production problems. It reduced that further to 30 million last week, leaving Ireland with about 45,000 fewer vaccines.

The difficulties with AstraZeneca supplies had already led the State to reduce its reliance on the vaccine from 40 per cent to 20 per cent of stocks. The Government was still depending on a steady supply from the company as part of its plans to ramp up the vaccine rollout to 250,000 vaccines a week from April.

Who has been receiving the AstraZeneca vaccines?

The vaccine has been given mostly to healthcare workers since it was introduced as the NIAC had recommended that the Pfizer and Moderna mRNA vaccines be preferred for the over 70s due to insufficient evidence of how effective the jab is in older people.

The latest HSE release giving the breakdown of Covid-19 vaccines shows that as of Wednesday, March 10th, some 109,352 AstraZeneca doses had been administered to people, compared with 442,485 Pfizer and 18,554 Moderna vaccines by that date.

Have there been side effects reported here?

Yes. The latest report on vaccine safety from the HPRA found that up to February 25th it had received 954 reports of suspected side effects from the AstraZeneca jab. A tenth or more of the suspected side effects reported were headache, muscle pain and pain in limbs, nausea and people feeling unwell and suffering a fever.

Less than 10 per cent of suspected side effects included altered taste, coughing or difficulty breathing, dizziness or an increased heart rate, joint pain, vomiting, weakness, tiredness, chills and feeling hot and cold, and sweating. The HPRA said that these were typical side effects and the majority were mild to moderate and were later resolved.

The HPRA has received a small number of reports of blood clots but that none are of a nature similar to those alerted by the Norwegian medicines agency.

Simon Carswell

Simon Carswell

Simon Carswell is News Editor of The Irish Times