typhoid vaccine live oral Ty21a

Ty21a typhoid vaccine (brand name: Vivotif) is a live attenuated oral vaccine used for active immunization against typhoid fever caused by Salmonella enterica serovar Typhi. Developed originally by the Swiss Serum and Vaccine Institute (later Berna Biotech, Crucell, PaxVax, Emergent BioSolutions, and currently owned and manufactured by Bavarian Nordic), the vaccine consists of the live attenuated Ty21a strain of S. Typhi. This strain is a chemically mutagenized galE mutant of the wild-type Ty2 strain, rendering it unable to synthesize the Vi capsular polysaccharide and making it harmless yet highly immunogenic. Upon oral administration, Ty21a replicates transiently in the intestinal tract, stimulating robust systemic and mucosal immune responses, including the production of IgA and IgG antibodies against S. Typhi O-lipopolysaccharide (O:LPS) and flagellar (H) antigens, as well as cell-mediated immunity. It is typically administered as enteric-coated capsules on alternate days (three or four doses depending on the country) and is widely used to protect travelers to endemic regions.

Brand names

VivotifTyphoral L

Other names

Ty21a typhoid vaccineTy-21a typhoid vaccineTy 21a typhoid vaccineTy21aTy-21aTy 21aSalmonella typhi Ty21a live attenuatedlive attenuated oral typhoid vaccine