Table 1. Keywords used to include studies in the literature review and to allocate studies to the relevant issue according to the WHO Vaccination Introduction Guidelines.

Key issues as per the WHO Vaccine Introduction Guidelines	Keywords used to classify studies to these issues
Public health priority	Priority, perception, Millennium Development Goals
Disease burden	Burden, incidence, prevalence, hospitalization, impact, mortality, cost, deaths, epidemiology, characteristic, etiology
Efficacy, quality and safety	Vaccine, efficacy, quality, safety, effectiveness, adverse event, standards, clinical trial
Other inventions	Antiviral, non-pharmaceutical
Economic and financial issues	Economic, budget, finance, funding, sustainability, cost-effectiveness, affordability, fiscal impact
Vaccine presentation	Presentation, formulation, dose
Supply availability	Supply, availability, manufacture, procurement, introduction strategy
Programmatic strength	Delivery, National Immunization Programme
Key issues as per the WHO Vaccine Introduction Guidelines	Keywords used to classify studies to these issues
Public health priority	Priority, perception, Millennium Development Goals
Disease burden	Burden, incidence, prevalence, hospitalization, impact, mortality, cost, deaths, epidemiology, characteristic, etiology
Efficacy, quality and safety	Vaccine, efficacy, quality, safety, effectiveness, adverse event, standards, clinical trial
Other inventions	Antiviral, non-pharmaceutical
Economic and financial issues	Economic, budget, finance, funding, sustainability, cost-effectiveness, affordability, fiscal impact
Vaccine presentation	Presentation, formulation, dose
Supply availability	Supply, availability, manufacture, procurement, introduction strategy
Programmatic strength	Delivery, National Immunization Programme