The Vi capsular polysaccharide vaccine (or ViCPS) is a typhoid vaccine recommended by the

World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level o ...

for the prevention of

typhoid Typhoid fever, also known as typhoid, is a disease caused by '' Salmonella'' serotype Typhi bacteria. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often there is a gradual onset of a high fever over several ...

(another is

Ty21a Ty21a is a live attenuated bacterial vaccine that protects against typhoid. First licensed in Europe in 1983 and in the United States in 1989, it is an orally administered, live-attenuated Ty2 strain of S. Typhi in which multiple genes, includin ...

). The vaccine was first licensed in the US in 1994 and is made from the purified Vi capsular polysaccharide from the Ty2 ''Salmonella'' Typhi strain; it is a

subunit vaccine A subunit vaccine is a vaccine that contains purified parts of the pathogen that are antigenic, or necessary to elicit a protective immune response. A "subunit" vaccine doesn't contain the whole pathogen, unlike live attenuated or inactivated v ...

Medical uses

The vaccine may be used in endemic areas in order to prevent typhoid. It is also commonly used to protect people who are traveling to parts of the world where typhoid is endemic.

Dosing

The vaccine is injected either under the skin or into a muscle at least seven days before traveling to the typhoid-affected area (the CDC recommend 14 days). The vaccine is not effective in children under the age of two. To maintain immunity, the vaccine should be repeated every three years.

Efficacy and duration of protection

The vaccine offers effective protection the first year after being given (with between 50% and 80% efficacy) and the second year (31% to 76%), but not after that.

Biology

The Vi polysaccharide, or Vi antigen, is part of the

bacterial capsule The bacteria capsule is a large structure common to many bacteria. It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell. It is a well-organized layer, not easily wash ...

found outside of the typhoid bacterium, ''Salmonella enterica'' subsp. ''enterica'' ser. Typhi. It is produced by the action of a single gene cluster in the cytoplasm and transported to the surface. This antigen contributes to much of typhoid's virulence, and is important for the infection of intestinal epithelial cells. It is also produced by ''S. enterica'' ser. Paratyphi C, the causative agent of paratyphoid fever C.

Trade names

* Typhim VI (manufactured by

Sanofi Pasteur Sanofi Pasteur is the vaccines division of the French multinational pharmaceutical company Sanofi. Sanofi Pasteur is the largest company in the world devoted entirely to vaccines. It is one of four global producers of the yellow fever vaccin ...

) * Typherix (manufactured by

GlaxoSmithKline GSK plc, formerly GlaxoSmithKline plc, is a British Multinational corporation, multinational pharmaceutical and biotechnology company with global headquarters in London, England. Established in 2000 by a Mergers and acquisitions, merger of Gl ...

)

Research

A newer conjugate form of the vaccine (Vi bound to a non-toxic recombinant ''

Pseudomonas aeruginosa ''Pseudomonas aeruginosa'' is a common encapsulated, gram-negative, aerobic– facultatively anaerobic, rod-shaped bacterium that can cause disease in plants and animals, including humans. A species of considerable medical importance, ''P. aer ...

exotoxin A The Pseudomonas exotoxin (or exotoxin A) is an exotoxin produced by ''Pseudomonas aeruginosa''. ''Vibrio cholerae'' produces a similar protein called the Cholix toxin (). It inhibits elongation factor-2. It does so by ADP-ribosylation of EF2 ...

, or Vi-rEPA) has enhanced efficacy, including protection of children under 5 years of age. The typhoid conjugate vaccine ("Typbar-TCV") is another Vi-based conjugate vaccine, in this case linked to

Tetanus toxoid Tetanus vaccine, also known as tetanus toxoid (TT), is a toxoid vaccine used to prevent tetanus. During childhood, five doses are recommended, with a sixth given during adolescence. After three doses, almost everyone is initially immune, but a ...

. It has been approved.

References

Subunit vaccines Typhoid fever {{Vaccine-stub