Mechanism of action

The ability of S. typhi to cause disease and to induce a protective immune response is dependent upon the bacteria possessing a complete lipopolysaccharide(1,2).

The S. typhi Ty21a vaccine strain, by virtue of a reduction in enzymes essential for lipopolysaccharide biosynthesis, is restricted in its ability to produce complete lipopolysaccharide (3,4). However, a sufficient quantity of complete lipopolysaccharide is synthesized to evoke a protective immune response.

VIVOTIF® oral vaccine is adsorbed in the proximal ileum, providing typhoid protection right where it's needed--in the GI tract. This live oral vaccine mimics actual clinical exposure, stimulating local, as well as, systemic immunity (5-9).

1. Germanier, R. Infect. Immun. 2:309-315,1970.
2. Germanier, R. E. Furer, Infect. Immun.4:663-673, 1971.
3. Germanier. R. E. Furer J. Infect. Dis.131:553-558, 1975.
4. Germanier, R. E. Furer Develop. Biol. Standard,43:3-7, 1983.
5. Cancellieri, V., Fara, G.M., J. Inf. Dis. (151)3, pp 482-484, 1985.
6. Tagiliabue, A., et.al., Clin Exp Immunol 62, pp 242-247, 1985.
7. D'Amelio, R., et.al., Infect Immun 56, pp 2731-2735, 1988.
8. Kantele, A.,Vaccine 8, pp 321-326, 1990.
9. Kantele, A., Mkel, P.H., Vaccine 9, pp 423-427, 1991.