Table 2

Study design and headline results

Authors	Study design	Evaluation details	Data source(s)
Comparison of vaccination types
Baio et al 23*	Evaluation type: CEA Measure of health benefit: deaths averted	Type of study: model-based economic evaluation (Bayesian network model) Perspective: healthcare provider Time horizon: NR Price year: NR	Observational study data from four GP databases over three influenza seasons was used for efficacy. The remainder of the evidence sources are unclear (not specified).
Meier et al 24	Evaluation type: CEA and CUA Measure of health benefit: QALYs gained	Type of study: model-based economic evaluation (Markov model) Perspective: healthcare provider (societal as a secondary analysis) Time horizon: lifetime Price year: 2012–2013	National data sources were used for incidence, costs, utilities, complications and mortality data. Vaccine efficacy was taken from a published review of studies from multiple countries/influenza seasons. Over-the-counter medication usage was estimated from previous publications.
Piercy et al (2004)25	Evaluation type: CEA Measure of health benefit: deaths averted and life-years gained	Type of study: model-based economic evaluation (decision tree) Perspective: healthcare provider Time horizon: lifetime Price year: NR	A variety of evidence sources were used, including national data, published literature and expert opinion. When French data could not be sourced (eg, hospitalisations), data from other European countries were used.
Comparison of vaccination strategies
Allsup et al 26	Evaluation type: CEA and CUA Measure of health benefit: deaths averted and QALYs gained	Type of study: RCT-based economic evaluation Perspective: healthcare provider Time horizon: lifetime Price year: NR	The main source of data was a prospective, single‐blind, randomised, placebo‐controlled clinical trial. Some parameters (eg, baseline hospitalisation rate) were supplemented with hospital data and/or clinician expert assumptions.
Brydak et al 29	Evaluation type: CUA Measure of health benefit: deaths averted, life-years gained and QALYs gained	Type of study: model-based economic evaluation (decision tree) Perspective: healthcare provider Time horizon: lifetime Price year: 2009	Published data specific to Poland were used to inform the model where possible. It was noted that, in some cases, Polish data were not available and US data had to be used (eg, hospitalisations).
Lugner et al 30	Evaluation type: CUA Measure of health benefit: QALYs gained	Type of study: model-based economic evaluation (dynamic transmission model) Perspective: healthcare provider and societal Time horizon: lifetime Price year: 2008	National data sources were used for demographic, resource use and cost data. Where evidence was not available for Germany and the UK, data from the Netherlands were used (eg, hospitalisations). Vaccine efficacy was taken from a published review and meta-analysis of studies from multiple countries/influenza seasons.
Postma et al 28	Evaluation type: CEA Measure of health benefit: life-years gained	Type of study: model-based economic evaluation (decision tree) Perspective: healthcare provider Time horizon: lifetime Price year: 1995	National data and published literature from the Netherlands were used for parameter values. Vaccine efficacy was taken from a published review and meta-analysis of studies from multiple countries/influenza seasons.
Scuffham and West31	Evaluation type: CEA Measure of health benefit: life-years gained and morbidity days saved	Type of study: model-based economic evaluation (decision tree) Perspective: healthcare provider Time horizon: lifetime Price year: 2000	Evidence sources included published studies, national databases and expert opinion. In some cases, country-specific data were not available for all parameters, and it was taken from another country in the study (eg, vaccine efficacy came from a US study).

*Note that the study by Baio et al 23 directly compared vaccination types, as well as comparing both vaccination types to no vaccination.23
CEA, cost-effectiveness analysis; CUA, cost-utility analysis; GP, general practitioner; NR, not reported; QALY, quality-adjusted life-year; RCT, randomised controlled trial.