Criteria to Determine the Need for new Vaccine Formulations or Methods of Vaccine Delivery

Objective

To identify essential criteria for assessing the need for new vaccine formulations or delivery systems.

Materials and Methods

The Delphi technique was used to identify the most important criteria. We developed a Likertscale based questionnaire, scoring each criterion on a scale of 1 (low) to 10 (high importance). The first version was completed by members of the WHO Product Development Group, with revisions administered to WHO-identified vaccine experts, classified by work site and affiliation. Within these strata, participants were randomly sampled and sent the online questionnaire's link. Highly important criteria were defined as a 25th percentile score of ≥8 and median score of 10.

Results

1163 experts were e-mailed, with 462 delivered. The questionnaire was completed by 182 (39%) respondents; 38 (21%) partial and 144 (79%) full answers. Respondents were from 55 countries and all WHO regions, representing academia (42%), health ministries (20%), industry (14%), WHO (6.5%), or other (17%), and had 15.6 mean years of experience.

Four criteria ranked first: 1) the disease's mortality rate; 2) coverage necessary to prevent transmission and anticipated improvement in coverage (of the new vaccines); 3) efficacy of current and alternative vaccines; 4) type and frequency of severe adverse events (AEFI) of current and new vaccines. Respondents preferred large increases in efficacy to decreases or minimal increases in cost of new vaccines compared to current vaccines.

Discussion

Vaccine-preventable diseases contribute importantly to the ten leading causes of death in the developing world. New vaccines or delivery mechanisms should have increased efficacy or coverage while maintaining low AEFIs and costs.