[Source: Eurosurveillance, full page: (LINK). Abstract, edited.]

Eurosurveillance, Volume 19, Issue 17, 01 May 2014 / Research articles

Investigation of an association between onset of narcolepsy and vaccination with pandemic influenza vaccine, Ireland April 2009-December 2010

D O?Flanagan <sup>1</sup><sup>,2</sup>, A S Barret<sup>1</sup><sup>,2</sup>, M Foley<sup>1</sup>, S Cotter<sup>1</sup>, C Bonner<sup>3</sup>, C Crowe<sup>4</sup>, B Lynch<sup>5</sup>, B Sweeney<sup>6</sup>, H Johnson<sup>7</sup>, B McCoy<sup>8</sup>, E Purcell<sup>4</sup>
<sup>1</sup>Health Service Executive, Health Protection Surveillance Centre, Dublin, Ireland - 2 These authors contributed equally to this manuscript ? 3 Department of Health, Dublin, Ireland - 4 Mater Private Hospital, Dublin, Ireland - 5 Children?s University Hospital Temple Street, Dublin, Ireland ? 6 Cork University Hospital, Cork, Ireland - 7 Health Service Executive, Health Intelligence Unit, Dublin, Ireland - 8 Our Lady?s Children?s Hospital, Crumlin, Dublin, Ireland
Citation style for this article: O?Flanagan D, Barret AS, Foley M, Cotter S, Bonner C, Crowe C, Lynch B, Sweeney B, Johnson H, McCoy B, Purcell E. Investigation of an association between onset of narcolepsy and vaccination with pandemic influenza vaccine, Ireland April 2009-December 2010. Euro Surveill. 2014;19(17):pii=20789. Available online: http://www.eurosurveillance.org/View...rticleId=20789 Date of submission: 26 April 2013
In 2011, the Irish Medicines Board received reports of onset of narcolepsy following vaccination against influenza A(H1N1)pdm09 with Pandemrix. A national steering committee was convened to examine the association between narcolepsy and pandemic vaccination. We conducted a retrospective population-based cohort study. Narcolepsy cases with onset from 1 April 2009 to 31 December 2010 were identified through active case finding. Narcolepsy history was gathered from medical records. Pandemic vaccination status was obtained from vaccination databases. Two independent experts classified cases using the Brighton case definition. Date of onset was defined as date of first healthcare contact for narcolepsy symptoms. Incidence of narcolepsy in vaccinated and non‐vaccinated individuals was compared. Of 32 narcolepsy cases identified, 28 occurred in children/adolescents and for 24 first healthcare contact was between April 2009 and December 2010. Narcolepsy incidence was 5.7 (95% confidence interval (CI): 3.4?8.9) per 100,000 children/adolescents vaccinated with Pandemrix and 0.4 (95% CI: 0.1?1.0) per 100,000 unvaccinated children/adolescents (relative risk: 13.9; absolute attributable risk: 5.3 cases per 100,000 vaccinated children/adolescents). This study confirms the crude association between Pandemrix vaccination and narcolepsy as observed in Finland and Sweden. The vaccine is no longer in use in Ireland. Further studies are needed to explore the immunogenetic mechanism of narcolepsy.