WHO preferred product characteristics for bivalent Salmonella Typhi/Paratyphi A vaccine for comprehensive protection against enteric fever- key considerations and research gaps.

Abstract

In 2021, Salmonella Paratyphi A caused >2 million illnesses, resulting in >14,000 deaths, most of which occurred among children under 5 years of age in socioeconomically deprived populations. Both typhoid fever and paratyphoid fever occur in such areas, but paratyphoid fever is currently concentrated in South Asia. Typhoid conjugate vaccines are recommended for the control of enteric fever in typhoid-endemic settings; however, there are increasing demands for the development of vaccines that can address enteric fever more broadly by including protection against paratyphoid fever. The WHO preferred product characteristics (PPC) and a research and development (R&D) technology roadmap are normative documents developed with the guidance and contribution of a multidisciplinary expert group following a standard methodological framework. In this paper, we summarize the PPC and R&D roadmap presenting the key attributes for a bivalent Salmonella enterica serovar Typhi and Paratyphi A vaccine, and discuss the identified key research and data gaps needed to optimize vaccine value and to inform public health and policy decisions, with a particular focus in paratyphoid and enteric fever endemic countries.