Vaccines against invasive Salmonella disease: current status and future directions

Abstract

Though primarily enteric pathogens, Salmonellae are responsible for a considerable yet under-appreciated global burden of invasive disease. In South and South-East Asia, this manifests as enteric fever caused by serovars Typhi and Paratyphi A. In sub-Saharan Africa, a similar disease burden results from invasive nontyphoidal Salmonellae, principally serovars Typhimurium and Enteritidis. The existing Ty21a live-attenuated and Vi capsular polysaccharide vaccines target S. Typhi and are not effective in young children where the burden of invasive Salmonella disease is highest. After years of lack of investment in new Salmonella vaccines, recent times have seen increased interest in the area led by emerging-market manufacturers, global health vaccine institutes and academic partners. New glycoconjugate vaccines against S. Typhi are becoming available with similar vaccines against other invasive serovars in development. With other new vaccines under investigation, including live-attenuated, protein-based and GMMA vaccines, now is an exciting time for the Salmonella vaccine field.

Keywords: GMMA; Salmonella; enteric; global health; glycoconjugate; nontyphoidal; typhoid; vaccines.

Figure 1. Geographical distribution of A. enteric fever and B. invasive nontyphoidal Salmonella (iNTS) disease indicating countries with high (> 100 cases/100,000 population/year) and medium (10–100 cases/100,000 population/year) disease burden. Based on data from refs.-

Figure 2. Established and new Salmonella vaccines, and how they relate to each other. (Adapted with permission from: MacLennan CA, Chapter 17 The challenge of developing global health vaccines against the invasive salmonelloses: enteric fever and invasive nontyphoidal Salmonella disease. Advanced Vaccine Research Methods for the Decade of Vaccines, Editors Bagnoli F, Rappuoli R, Publisher Caister Academic Press.)