Immunization, Vaccines and Biologicals


Typhoid fever is a systemic infection caused by Salmonella Typhi, usually through ingestion of contaminated food or water. The acute illness is characterized by prolonged fever, headache, nausea, loss of appetite, and constipation or sometimes diarrhoea. Symptoms are often non-specific and clinically non-distinguishable from other febrile illnesses. However, clinical severity varies and severe cases may lead to serious complications or even death. It occurs predominantly in association with poor sanitation and lack of clean drinking water. According to the most recent estimates (published in 2014), approximately 21 million cases and 222 000 typhoid-related deaths occur annually worldwide. A similar but often less severe disease, paratyphoid fever, is caused by Salmonella Paratyphi A, B or C.

Two typhoid vaccines are currently recommended for use by:

  • an injectable polysaccharide vaccine based on the purified Vi antigen (known as Vi-PS vaccine) for persons aged two years and above;
  • and a live attenuated oral Ty21a vaccine in capsule formulation for those over five years of age.

WHO recommends the use of the Vi-PS and Ty21a vaccines to control endemic disease and for outbreak control. WHO further recommends that all typhoid fever vaccination programmes should be implemented in the context of other efforts to control the disease, including health education, water quality and sanitation improvements, and training of health professionals in diagnosis and treatment.

Several Vi polysaccharide–protein conjugate vaccine candidates are under development (or are nationally licensed but not on the international market) and anticipated to be available in the future for infant immunization.

WHO position papers

Prequalified vaccines

Further information

Related partner links

Last updated: 13 April 2015