Ty21a

Ty21a is a live attenuated bacterial vaccine used to prevent typhoid fever. It was developed by Swiss Serum and Vaccine Institute and is marketed under the brand name Vivotif.

History

Ty21a was first licensed in Europe in 1983 and in the United States in 1989. It was developed as a response to the high incidence of typhoid fever in developing countries and the increasing resistance of the Salmonella Typhi bacteria to antibiotics.

Mechanism of action

Ty21a works by stimulating the immune system to produce an immune response against the Salmonella Typhi bacteria. The vaccine contains a weakened strain of the bacteria that does not cause disease but is able to provoke an immune response.

Administration

Ty21a is administered orally, usually in the form of a capsule. The recommended dosage is one capsule taken every other day for a total of four doses. The vaccine should be taken with a cold or lukewarm drink approximately one hour before a meal.

Efficacy and side effects

Studies have shown that Ty21a is between 50% and 80% effective at preventing typhoid fever. The most common side effects are stomach pain, nausea, and fever. Serious side effects are rare.

See also

• Vaccine
• Typhoid fever
• Salmonella typhi