A brief review on the immunological scenario and recent developmental status of vaccines against enteric fever.

Enteric fever has been one of the leading causes of severe illness and deaths worldwide. S. Typhi and S. Paratyphi A, B and C are important enteric fever-causing organisms globally. This infection causes about 21 million cases among which 222,000 typhoid related deaths occurred in 2015. These estimates do not reflect the ultimate and real status of the disease due to the lack of unified diagnostic and proper reporting system from typhoid endemic and other regions. Current control strategies have become increasingly ineffective due to the emergence of multi-drug resistance among the strains. This situation worsens the disease-burden in developing as well as in developed countries. Moreover the emergence of S. Paratyphi A as a major enteric fever-causing organism in several Asian countries, demands a prophylactic measure at this hour. Other than two licensed vaccines of S. Typhi, there are no exsisting vaccines for S. Paratyphi A. Moreover, travelers returning from endemic regions are becoming more susceptible to have these infections. In this situation, a need for bivalent approach is required where a single immunogen (consisting from each organism) will be effective against the disease. In this review, we have focused on the general information about typhoidal fever, its spread and epidemiology in brief and the present status of typhoidal vaccines and its future. This review highlights existing gaps in the typhoidal salmonellae research with a special emphasis on the status of present typhoidal salmonellae vaccine research.