Table 2.

Definition of feasibility

	Definition
Biological feasibility	Considers progression of clinical development; existence of immunity from natural exposure; current understanding of mechanisms of immunity; and the likelihood of a vaccine protecting against most pathogenic strains
Product development feasibility	Considers the existence of established animal and in-vitro models to facilitate vaccine development; the ease of clinical development and setting a late-stage clinical trial; and the availability of human challenge models if these are likely to be required
Access and implementation feasibility	Considers the possibility of implementation within existing delivery systems, in particular childhood immunisation programmes; commercial attractiveness and whether there are likely to be high-income markets to support tiered pricing; the clarity of the licensure and policy decision pathway; and the ease of uptake and acceptability in target populations

Each aspect was rated from very low to very high feasibility.¹⁷