Parents suing the state over side-effects from a swine flu vaccine say that the jab was rushed into use before getting full approval.
It is alleged that the Pandemrix vaccine caused the sleep disorder Narcolepsy in a number of children.
The condition makes sufferers suddenly fall asleep without warning.
Dr Eleanor Galvin says a big rise in the condition was noted around the time the vaccine was being administered.
"Kids were vaccinated in 2009 and shortly after that Narcolepsy - which was a really rare thing that you would very rarely have a patient with Narcolepsy - it suddenly became more common," said Dr Galvin.
"Sleep specialists, instead of seeing two or three a year, were seeing 20."
Tom Matthews, Co-Founder of Sound - Sufferers of Unique Narcolepsy Disorder, said: "There was a stampede by the Irish government to get the vaccine and there were no trials carried out.
"They didn't tell the public that the trials weren't carried out.
"In fact, the Irish Medicine Board in September 2016 didn't endorse the vaccine."