"In my opinion we can now say it, it is clear that there is an association with the vaccine". What causes this reaction, however, we still do not know.
The regulator has consistently said the benefits outweigh the risks as it investigates 44 reports of an extremely rare brain clotting ailment known as cerebral venous sinus thrombosis (CVST) out of 9.2 million people in the European Economic Area who have received the AstraZeneca vaccine.
A senior official in the agency said in an interview published on Tuesday that there seemed to be a connection, although it was unclear how this happened.
These cases were spread across 2.8 million AstraZeneca vaccine doses injected, or just over one case per 100,000 doses.
"We are trying to get a precise picture of what is happening, to define in detail this syndrome due to the vaccine", Cavaleri said. A causal link with the vaccine is not proven, but is possible and further analysis is continuing, the agency said.
The EMA said the vaccine was not associated with an increase in the overall risk of blood clots, but may be associated with clots linked to very rare condition involving low levels of blood platelets (thromocytopenia).
Questions about serious blood clots in a tiny minority of cases have undermined confidence in the AstraZeneca vaccine.
So far in Ireland, over 203,000 doses of the AstraZeneca vaccine have now been administered.
An investigation is also underway in the United Kingdom, where researchers are looking at the possibility of links between the AstraZeneca vaccine and rare blood clots. Many countries have already begun to restrict the use of the vaccine in younger people.
In total, the United Kingdom has ordered 457 million doses, of which 100 million are from AstraZeneca.
Twomey also blamed the slow rollout on a lack of co-ordination between the Australian national government and states, with the latter complaining about slower-than-expected distribution and a lack of certainty on vaccine supplies.
The EMA last week recommended that countries should keep using the AstraZeneca vaccine because the benefits outweighed the risks, as countries including Italy suspended their rollout of the jab. There have been seven deaths among the 30 cases.