Authorities in Britain are examining a possible link between the AstraZeneca coronavirus vaccine and a 'rare clotting disorder'.
It comes after a senior official from the European Medicines Agency (EMA) suggested the available evidence indicates 'a clear link' between the vaccine and rare blood clot events.
The EMA has yet to respond to the claim.
Meanwhile a trial of the drug on children in the UK has been paused, while the country's medicines regulator - the Medicines and Healthcare products Regulatory Agency (MHRA) - carries out an investigation.
Over the weekend, it was reported that there had been 30 blood clotting cases recorded by the MHRA out of more than 18 million doses of the AstraZeneca shot administered.
The UK agency confirmed that of those 30 people, seven had died as of March 24th.
The World Health Organisation (WHO) maintains that the benefits of this vaccine outweigh any risks.
Paul Moynagh is professor of immunology and director of the Kathleen Lonsdale Institute for Human Health Research at Maynooth University.
He told Newstalk Breakfast people should keep perspective.
"First of all it's important to say when there's a sense that there may be some reaction to vaccines that this is studied in detail, and that's what's being done at the moment.
"There was a report yesterday - an official from the EMA had indicated there was a link.
"The EMA has to formally respond to that and I think it's due to give a report in the coming days."
Prof Moynagh said an earlier analysis found that incidence of common clotting disorders with the AstraZeneca vaccine "is the same as in the background population that hasn't been vaccinated.
"But in the last number of weeks, there's a rare clotting disorder - especially in the brain, in the vein that drains the blood from the head and the face - and there seems to be at least an increase in incidents.
"It's very rare".
'Benefits far outweigh risks'
He said in the UK, where 18 million people have been vaccinated with AstraZeneca, there have been cases "in the mid-20s".
"They're looking at that now in more detail", he said.
"Even with those numbers, certainly the WHO announced yesterday - and it's probably likely the EMA will come out with the same conclusion - that still the benefits far outweigh the risks.
And Prof Moynagh said people should be looking at the 'orders of magnitude'.
"Even in the UK, it's sort of less than one in a million - some European countries are coming in... at maybe one in 200,000.
"So there is still a big difference... and the association has to be proved, and there's research going on in terms of trying to get a better understanding in terms of if there is an association why the vaccine may be triggering this very rare disorder.
"I should say as well that's more common in younger people, less than 50, and especially in women.
"It seems to resemble quite a rare clotting disorder that some people get in response to heparin, which is actually used as an anticoagulant."
Ireland and AstraZeneca
Ireland paused its AstraZeneca rollout for a time last month amid concerns over the drug.
Dr Colm Henry, Chief Clinical Officer with the HSE, said at the time that confidence in the vaccine programme was important.
"I think given the nature of these conditions - a small number, yes in younger people, but a rare clotting conditions - there may well be no association, no cause and effect proven with the vaccine.
"But I think it was a prudent and correct thing to do to pause temporarily - as other countries have done", he said.
While the EMA subsequently said the vaccine was safe and effective.
It concluded the jab was not associated with an increase in the overall risk of blood clotting, although it could not rule out definitively a link between the vaccine and rare clotting cases.
Additional reporting: IRN