Preferred product characteristics (PPCs) describe WHO preferences for parameters of vaccines, in particular its indications, target groups, possible immunization strategies, and features of clinical data desired related to safety and efficacy. These preferences are shaped by the unmet public health need in a priority disease area for which WHO encourages vaccine development. In keeping with its mandate, WHO preferences reflect its desire to promote the development of vaccines with high public health impact and suitable for use in low to middle-income countries. 

PPCs are meant to provide early guidance for the development of new products or the improvement of existing ones. Each PPC addresses early stage vaccine R&D generally at least 5-10 years from vaccine availability, and will be reviewed and updated if necessary at least every 5 years. PPC are not static exit criteria, but are structured in such a way so as to drive innovation towards meeting public health needs.