Ty21a

Ty21a Vaccine

Ty21a oral vaccine blister pack

The Ty21a vaccine is an oral vaccine used to prevent typhoid fever, a disease caused by the bacterium Salmonella enterica serotype Typhi. It is one of the two main types of typhoid vaccines, the other being the Vi capsular polysaccharide vaccine.

Development

The Ty21a vaccine was developed in the 1970s and 1980s as a live attenuated vaccine. It was designed to provide immunity by mimicking a natural infection without causing the disease. The vaccine strain, Ty21a, is a mutant of Salmonella Typhi that lacks the ability to produce certain enzymes necessary for its virulence.

Administration

The Ty21a vaccine is administered orally in the form of enteric-coated capsules. The standard regimen consists of three to four doses taken on alternate days. It is recommended for travelers to areas where typhoid fever is endemic, as well as for people living in such areas.

Mechanism of Action

The vaccine works by stimulating the body's immune system to recognize and fight the Salmonella Typhi bacterium. Upon ingestion, the attenuated bacteria in the vaccine colonize the gut, prompting an immune response that includes the production of antibodies and activation of T cells.

Efficacy

The Ty21a vaccine has been shown to provide moderate protection against typhoid fever. Its efficacy varies depending on the population and the level of exposure to the bacterium. Protection typically lasts for about five years, after which a booster dose may be required.

Safety

The Ty21a vaccine is generally well-tolerated. Common side effects include mild gastrointestinal symptoms such as nausea and abdominal discomfort. Serious adverse reactions are rare.

Related Pages

• Typhoid fever
• Salmonella enterica
• Vi capsular polysaccharide vaccine
• Vaccination