Immunization, Vaccines and Biologicals


Typhoid fever is an infection caused by the Salmonella typhi bacterium, 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. However, clinical severity varies and severe cases may lead to serious complications or even death. WHO estimates that 21 million typhoid cases and 216 000–600 000 typhoid-related deaths occur annually worldwide. A similar but often less severe disease is caused by Salmonella paratyphi bacteria.

Two typhoid vaccines are available internationally and both are considered safe and effective:

  • An injectable polysaccharide vaccine based on the purified Vi antigen (known as Vi-PS vaccine) for children under two years of age.
  • A live attenuated oral Ty21a vaccine currently available in capsules 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

Vaccine use/schedule

Disease burden/surveillance

Prequalified vaccines


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Last updated: 28 November 2013


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