A CORONER has concluded it is "most likely" that a nursery nurse developed the sleep disorder narcolepsy as a result of receiving a swine flu vaccination.
Recording a narrative conclusion, Paul Cooper, acting senior coroner for South Lincolnshire, said studies showed there were "significantly raised odds of narcolepsy after [being given the] Pandemrix" vaccine in those aged 18 and above.
"On the available evidence on the association between vaccination with Pandemrix and onset of narcolepsy it seems most likely that receipt of this vaccine in December 2009 caused Miss Clack's narcolepsy," said Mr Cooper.
He added that narcolepsy triggers depression, though he noted the case of Miss Clack was "complex and very rare".
Katie Clack and her family celebrating father's day in 2013
Miss Clack's family is represented by Peter Todd and Freya Colvin, of law firm Hodge Jones & Allen.
Narcolepsy turned her life into a terrible daily struggle
A statement issued on behalf of the family said: "Katie was an energetic young woman who had just discovered her passion working with children.
"Narcolepsy turned her life into a terrible daily struggle and drastically reduced her quality of life.
"We cannot believe she would have decided to take her own life had the balance of her mind not been disturbed."
Miss Colvin added: "The Clack family has waited a long time for this inquest.
"It is important that the coroner has recognised the causal link between the vaccine and narcolepsy and the devastating impact this had on Katie's short life."
Katie Clack, then aged three, and older sister Emma Sutton, then aged four
Earlier this year a boy who developed the sleeping disorder caused by the swine flu vaccine was awarded £120,000 in damages.
Josh Hadfield, 10, from Frome in Somerset, developed narcolepsy after receiving the Pandemrix vaccine six years ago.
In 2013, lawyers launched a class action on behalf of 38 Britons – including 19 children – who developed narcolepsy after having the vaccine.
Scientists from the former Health Protection Agency (HPA) said there was evidence of a link between the Pandemrix jab – manufactured by GlaxoSmithKline(GSK) - and narcolepsy in children.
HPA figures suggested one in 55,000 children vaccinated - about 20 in the UK – are thought to have developed narcolepsy.
The nursery nurse with her two nieces Jasmine (left), and Lily (right)
Josh was awarded the money after an appeal against the Government, which had initially refused to pay as he was not "severely disabled" enough.
Speaking at the time, a spokesman for GlaxoSmithKline said: "We remain committed to carrying out additional research into the potential role of Pandemrix in the development of narcolepsy."
It was also supporting investigations into reported cases.
Across Europe, about 31 million people are thought to have received the Pandemrix jab.
Narcolepsy is a rare but serious neurological disorder that affects about 31,000 people in Britain.
The condition can cause massive disruption to sleep and daily life.
A Department of Health spokesman said: "Katie's death was tragic and we offer our sympathies to her family. Pandemrix vaccine was used to prevent serious illness and deaths during the swine flu pandemic in 2009/10. At the time, the possible association with narcolepsy was not known."