Immunization, Vaccines and Biologicals

Yellow Fever

Yellow Fever (YF) is a mosquito-borne viral disease of humans and other primates, and is currently endemic in over 43 countries in the tropical regions of Africa and The Americas. Infection with the YF virus can be asymptomatic or cause a wide spectrum of disease, from mild symptoms to severe illness with bleeding, jaundice and, ultimately, death. Over 30,000 deaths occur each year and this figure would be much higher without vaccination. Aedes aegypti, is the most important vector. Transmission is complex with different characteristics in different endemic areas.

All currently available yellow fever vaccines are live, attenuated and based on the 17D attenuation variant. Vaccines from four manufacturers are currently prequalified by WHO.

Yellow fever vaccination is carried out for 3 reasons: to protect populations living in areas subject to endemic and epidemic disease; to protect travellers visiting these areas; and to prevent international spread by minimizing the risk of importation of the virus by viraemic travellers.

A single dose of YF vaccine is sufficient to confer sustained life-long protective immunity against YF disease. In view of the ongoing transmission of YF virus, and the proven efficacy and safety of YF vaccination, WHO recommends that all endemic countries should introduce YF vaccine into their routine immunization programmes. Vaccine should be offered to all unvaccinated travellers aged >9 months, travelling to and from at-risk areas, unless they belong to the group of individuals for whom YF vaccination is contraindicated.

Well designed and adequately powered studies are needed to assess co-administration of YF vaccine with other live vaccines, including MMR, and to assess safety and immunogenicity of YF vaccine in pregnant women, in people aged ≥60 years, and in HIV positive adults with CD4 T cell values >200 per mm(3).

WHO position papers

Prequalified vaccines

Further information

Related links

Last update: 29 January 2014

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