Q&A: Is the AstraZeneca Covid-19 vaccine safe for older people?

Firm facing complaints over delivery pledges but also reports of possible side effects

The AstraZeneca Covid-19 vaccine developed with scientists at Oxford University continues to be in the news for all the wrong reasons.

From being in prime position in the race to create a vaccine, the company has become embroiled in a bitter dispute over supply. And recent reports over possible side effects associated with its use have compounded matters.

In between, there was protracted debate about its effectiveness in older people. A particular problem arose in the way its developers conducted initial clinical trials because they did not include older people. It culminated in the European Medicines Agency, the EU regulator, approving its use – yet some countries then declined to deploy it for older cohorts.

Based on a lack of evidence, Ireland's National Immunisation Advisory Committee (Niac) in early February advised that the Pfizer-BioNTech and Moderna mRNA vaccines should be given to over-70s "where practicable", but that vaccination should not be delayed.


The Department of Health subsequently adopted a less-nuanced position, saying only those vaccines should be administered to over-70s.

Niac updated its advice on Friday recommending the AstraZeneca vaccine also be administered to over-70s in the State.

However, on Sunday, the advice changed again, and use of the AstraZeneca jab for all age groups was suspended temporarily, after the Norwegian Medicines Agency reported four serious blood clotting events in adults after vaccination.

What changed in the month to last Friday?

There were reports in three scientific publications on "real-world effectiveness" on how the vaccine performs in older people, Niac chairwoman Karina Butler said on Friday.

Positive data from Scotland, in particular, has provided more flexibility, she said. This research confirmed equal efficacy in over-70s and therefore gave more flexibility for the vaccine's use in all age groups.

What does the AstraZeneca vaccine bring to the table?

It harnesses a virus to act as a Trojan horse that sneaks some of the genetic blueprint for Covid-19 into the body. The “viral vector” used is a modified common cold virus to provoke an immune response.

Clinical trials found with two doses it was 62 per cent effective. But when people were given a half dose followed by a full dose at least a month later its efficacy rose to 90 per cent.

Some questioned these results, including the UK medicines regulator, which recommended two full doses be administered in approving its use. It concluded it was up to 80 per cent effective when the second dose was delayed by three months. Delaying the second dose in the UK allowed the NHS to prioritise delivery of the first dose to as many people as possible.

The benefits of this vaccine are considerable. It is much easier to administer and can be stored at normal refrigerator temperatures for at least six months.

What of blood clot concerns being raised in some countries?

Instead of full steam ahead while trying to address supply chain blockages, another issue in the form of a potential health scare has arisen. Over the past week, a growing number of countries have suspended their rollouts of the jab because of reported cases of blood clots supposedly linked to vaccination.

The European Medicines Agency said last Friday there had been 30 cases of "thromboembolic events" reported among five million people who had received the jab in Europe. But, significantly, it has not called for it to be withdrawn from use; in other words, benefits outweigh risks.

There have been more than 11 million doses of the vaccine administered in the UK and no reports of excess deaths or blood clots among those receiving the vaccine, compared with the expected rate in the population.

There is no established link between the vaccine and blood clots, though each case requires careful investigation.

Should older people feel safe if they are offered the vaccine?

The overwhelming scientific opinion is that it is safe for all age groups. Indeed, all three vaccines in circulation currently are 100 per cent effective in reducing severe Covid-19 infection and deaths. They will soon be joined by the Johnson & Johnson vaccine, while the Novavax jab looks set to be the next to be approved.

A UK study published in early March found the Pfizer and AstraZeneca vaccines are effective in significantly reducing Sars-CoV-2 infection in older adults and in providing long-term protection.

The bottom line is the public should have confidence current vaccines are safe and highly effective. The temporary suspension of the use of the AstraZeneca vaccine here is designed to strengthen public confidence in the rollout, Prof Butler said.

Who decides who gets what vaccine?

The HSE – backed by National Public Health Emergency Team, Niac and the vaccination taskforce – are involved in a huge logistical effort to get the Irish population vaccinated as quickly as possible. At EU and Government level, intensive efforts are being made to improve supply chains.

This does not provide the luxury of pick and choose when offered a vaccine; given proven effectiveness and risk profile of currently approved jabs.

When asked about patients refusing the AstraZeneca vaccine, Prof Butler said such refusals were based on a lack of understanding and confirmed there would not be a choice. She encouraged patients to take what they were offered, as all were very effective.

How much easier will vaccination rollout be with the AstraZeneca vaccine available for older people?

The obvious versatility and flexibility of the vaccine will significantly assist Ireland’s vaccination programme. It is especially suited for deployment in care settings and GP surgeries.

But it will require a careful recasting of vaccination schedules backed by guarantees on supply, to reduce risk of heightened concerns or lack of confidence among the public.

“We are now spoiled for choice with vaccines . . . It is down to logistics and when they will be delivered,” said Prof Butler on Friday.

The longer time between doses of AstraZeneca is also an advantage as it gave the opportunity for more people to be vaccinated, as the first dose provides significant immunity.

On Sunday, Prof Butler said she hoped the reports from Norway were just an overreaction and that a decision would be made concerning the safety of the vaccine within the week.