Landscape analysis of invasive non-typhoidal salmonella (iNTS) disease and iNTS vaccine use case and demand: Report of a WHO expert consultation.

Invasive disease caused by non-typhoidal Salmonella serovars (iNTS) occurs with increased risk in the presence of other comorbidities such as malaria, HIV, malnutrition, anaemia and sickle cell disease. While infection with non-typhoidal (NTS) serovars often results in self-limited enterocolitis in high-income settings, in sub-Saharan Africa (SSA) where these risk-comorbidities are common, an invasive (iNTS) disease phenotype is seen, associated with up to 20 % case-fatality ratio, and antimicrobial resistance is both significant and growing. The need to evaluate the potential public health value of vaccines against iNTS disease is increasingly being recognized, and several candidate vaccines are in early development. A better understanding of the global burden and epidemiology of iNTS disease, as well as the potential public health and socio-economic benefits that iNTS vaccines may offer is fundamental to support and justify the investments in vaccine development. In addition, the pathways for licensure, policy recommendations and eventual vaccine prioritization and use in low- and middle-income countries (LMICs) need to be defined. Here, we report on the proceedings of an expert consultation held on 29 November - 1 December 2021 as part of an overall project to develop a Full Value of Vaccines Assessment (FVVA) for iNTS vaccines and in addition to more recent iNTS vaccine developments. Experts at the consultation reviewed the current evidence on iNTS disease and discussed knowledge gaps to be addressed to accelerate vaccine development, licensure and introduction, as well as LMIC perspectives on potential iNTS vaccine use and demand. The learnings from this consultation are critical inputs to inform remaining work under the iNTS FVVA project.