Table 1.

Comparison of study design between inpatient and outpatient settings from 14 publications.

Study	Country	Season	Setting	Case definition	Interval since onset	Dominant type/subtype^b	Vaccine match^c	Time in model	Comorbid in model	% with high-risk condition
Cheng et al. [12]	Australia	2010	Inpatient	Admission	Unrestricted	H1pdm	Yes	Fortnight	Yes	79%
Levy et al. [13]	Western Australia		Outpatient	ILI	≤4d			Week	No	NA
Fielding et al. [20]	Victoria, Australia		Outpatient	ILI	≤4d			Month	No
Kwong et al. [14]	Ontario, Canada	2010–2011	Inpatient	Admission	Unrestricted	H3	Yes	Month	Yes	≥72.8%^d
Skowronski et al. [15]	Canada		Outpatient	ILI	≤7d			Week	Yes	34.9%
Puig-Barberàet al.^a [16]	Valencia, Spain	2011–2012	Inpatient	ILI	Not specified	H3	No	Week	No	88%
Jimenez-Jorge et al.^a [17]	Spain		Outpatient	ILI	≤7d			Week (cat)	No	62.9%
Talbot et al. [18]	Tennessee, USA	2011–2012	Inpatient	ARI	≤10d	H3	No	Onset to admission	Yes	86%
Ohmit et al. [19]	USA		Outpatient	ARI	≤7d			Fortnight	Yes	25.4%
Cheng et al. [21]	Australia	2012	Inpatient	Admission	Not specified	H3	No	Not specified	Yes	83.2%
Sullivan et al. [22]	Australia		Outpatient	ILI	Not specified			Month	No	NA
Martinez-Baz et al. [10]	Narrava, Spain	2012–2013	Inpatient	ILI	≤7d	B	Yes	Month	Yes	NA
Martinez-Baz et al. [10]	Narrava, Spain		Outpatient	ILI	≤7d			Month	Yes	NA
Turner et al. [9]	Auckland, New Zealand	2013	Inpatient	SARI	≤7d	H3	Yes	Week	Yes	64.5%
Turner et al. [9]	Auckland, New Zealand		Outpatient	ILI	≤7d			Week	Yes	NA
Pierse et al. [23]	Auckland, New Zealand	2014	Inpatient	SARI	≤7d	H1pdm	Yes	Timing of the intervention to peak of season	Yes	51%
Pierse et al. [23]	Auckland, New Zealand		Outpatient	ILI	≤7d			Timing of the intervention to peak of season	Yes	26%

Enrolled patients targeted for influenza vaccination. Cases were positive for influenza A(H3N2) virus.

Information retrieved either from studies or the WHO website.

72.8% was the percentage of subjects with chronic cardiovascular disease.