Table 1 Inclusion and exclusion criteria

Population of interest

Adults ≥65 years old, irrespective of setting

Adults < 65 years old

Children

Studies that only include specific subpopulations irrelevant for study aim (i.e. diabetes, HIV)

Intervention of interest

Seasonal influenza vaccination

Interventions not related to seasonal influenza, (AH1N1, pandemic or epidemic periods, vaccine shortage)

Actions to address barriers against vaccination (i.e. advertising, provider mailings, patient and staff education, visiting nurses)

Comparisons of interest

Not been immunized

Different vaccines

Populations without access to immunization

Outcome measures of periods before seasonal immunization campaigns

Populations or groups without the intervention that promote immunization or avoid barriers

Exposures of interest

Barriers against vaccination

Social determinants of health

• Socio-economic & political context: governance, policy (macroeconomic, social, health), cultural and societal norms and values

• Social position: education, occupation, income, gender, ethnicity/race

• Material circumstances, social cohesion, psychosocial factors, beliefs, behaviours, biological factors

• Health care system, distribution of health and well-being

Outcome of interest

Vaccine coverage

Pharmacological aspects of the vaccine

Study designs

Qualitative (case-studies, ethnography, grounded theory, phenomenology; or specific techniques as focus groups, in-depth interviews, surveys, participant observation)

Reviews, cost-effectiveness or economic analyses

Quantitative (descriptive, cross sectional, case–control, cohort, randomized controlled trial), mixed-methods