The present invention relates to the modification of a live attenuated strain of Salmonella enterica serovar Typhi, wherein its natural surface-exposed polysaccharide and flagellin antigens may be converted to, or augmented by, those from other strains of Salmonella, including S. enterica serovars Paratyphi, Typhimurium and Enteritidis. The present invention also relates to modified strains of Salmonella enterica serovar Typhi being suitable for use as components of a vaccine for enteric fever and salmonellosis.
