ba Gilca 2011.

Methods	Matched case‐control study performed to assess the effectiveness of a single paediatric dose of AS03‐adjuvanted vaccine (Pandemrix, GSK) against hospitalisation in children aged 6 months to 9 years during the fall 2009 vaccination campaign in Quebec, Canada
Participants	Description of cases: children hospitalised for PCR‐confirmed pH1N1 infection (“Quebec residents aged 6 months to 9 years hospitalised with laboratory‐confirmed pH1N1 infection”) Description of controls: non‐hospitalised children, matched by age and region of residence. For each case, 15 potential controls were selected at random from the health insurance registry.
Interventions	A single paediatric dose of AS03‐adjuvanted pH1N1 vaccine vs no intervention
Outcomes
Funding Source	Government
Notes	The authors conclude that a single paediatric dose of the AS03‐adjuvanted pH1N1 vaccine given to children aged 6 months to 9 years is highly protective against hospitalisation, beginning as early as 10 days after immunisation. The study is summarily reported. It is unclear whether blinded assessment of exposure status was carried out. In addition, it is unclear whether the children were hospitalised because of influenza or whether influenza was a chance finding and hospitalisation occurred for other reasons. This is a very important aspect in pandemic H1N1 infection, where most deaths were recorded for multiple pathologies.
Risk of bias
Bias	Authors' judgement	Support for judgement
CC‐Case Selection	Low risk	Independent validation
CC‐Control Selection	Low risk	Community control
CC‐Comparability	Unclear risk	Drawn from insurance registry
CC‐Exposure	Unclear risk	Self reported
Summary assessments	Unclear risk	Plausible bias that raises some doubts about the results