cb O'Flanagan 2014.

Methods	Large retrospective, population‐based cohort study assessing the possible association between monovalent, pandemic, H1N1 flu vaccine Pandemrix (GSK) and narcolepsy
Participants	Virtually the whole population of Ireland is included in the study, which consists of 90,280 children and adolescents aged below 20 and 3,325,643 adults.
Interventions	Exposure to Pandemrix between October 2009 and March 2010. Information on vaccination was collected in 1 of 2 databases, depending on where vaccination was administered: vaccinations performed in general practitioner clinics were registered in the primary care reimbursement service (PCRS) database, and those performed in Health Service Executive mass vaccination clinics in the pandemic data management system (PDMS) database. The number of individuals vaccinated with Pandemrix was extracted from these databases by week of vaccination. The number of unvaccinated individuals was computed by subtracting the number of individuals vaccinated with any pandemic vaccine brand from the total number of individuals reported in the 2011 census.
Outcomes	Narcolepsy: cases have to fulfil the definition of levels 1 to 3 from Brighton Collaboration. Level 1: Excessive daytime sleepiness AND/OR suspected cataplexy AND cerebrospinal fluid hypocretin‐1 deficiency. Level 2: Excessive daytime sleepiness AND definite cataplexy AND level 1 or 2 Multiple Sleep Latency Test abnormalities (mean sleep latency < 8 minutes for adults and < 12 minutes for children < 16 years AND/OR at least 2 sleep‐onset REM periods). Level 3: Excessive daytime sleepiness AND level 1 Multiple Sleep Latency Test abnormalities (mean sleep latency < 8 minutes for adults and < 12 minutes for children < 16 years AND at least 2 sleep‐onset REM periods). Narcolepsy cases were identified by means of active case finding by contacting all sleep clinics, neurologists, paediatricians, GPs, psychiatrists, psychologists, and public health nurses in Ireland. 2 experts (1 adult and 1 paediatric neurologist who were blinded to the vaccination status of the cases) reviewed the clinical history of narcolepsy cases (medical records and clinical charts) to confirm the diagnosis and classify them using the internationally agreed Brighton Collaboration case definition for narcolepsy. Cases were included in the study if: their date of first symptom of narcolepsy recorded in medical files occurred after 1 April 2009 and before 31 December 2010; cases or guardians gave oral informed consent; they were classified as level 1, 2, or 3 as per the Brighton case definition. Prevalent cases with onset prior to April 2009 were excluded. The date of first contact with health care for narcolepsy symptoms as retrieved from GP notes and clinical records was used to estimate the onset of narcolepsy in primary analysis.
Notes	Funding source ‐ government
Risk of bias
Bias	Authors' judgement	Support for judgement
PCS/RCS ‐ selection exposed cohort All outcomes	Low risk	Virtually the whole Irish population is included.
PCS/RCS ‐ selection non‐exposed cohort All outcomes	Low risk	Drawn from the same source
PCS/RCS ‐ comparability All outcomes	Unclear risk	Possible confounders have been taken into account.
PCS/RCS ‐ assessment of outcome All outcomes	Low risk	Clinical information of possible cases were reviewed, and the correspondence to a standard case definition verified.
Summary assessment	Unclear risk	Low risk of bias