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Yellow fever is a zoonosis indigenous to some tropical regions of South America and Africa which has caused numerous epidemics with high mortality rates throughout history. Its etiologic agent is the yellow fever virus, an arbovirus of the genus Flavivirus (family Flaviviridae). Transmission occurs through the bite of certain species of mosquitoes: In jungle areas of South America, by mosquitoes of the Haemagogus and Sabethes genera. In urban and certain rural areas, the bite of infective Aedes aegypti mosquitoes.

Yellow fever can be prevented with live-attenuated yellow fever vaccine 17D, which is considered safe and effective, and has been used for over 60 years to actively immunize children and adults against infection with the yellow fever virus. It confers lasting immunity, perhaps for life.

Yellow fever vaccination strategies implemented in the Region of the Americas include: 1) introduction of yellow fever vaccine into national immunization programs in all endemic countries for children aged 1 year; 2) vaccination campaigns during inter-epidemic periods; 3) vaccination campaigns in response to outbreaks or epizootics; and 4) vaccination of travelers entering enzootic areas, except when contraindicated.

It is recommended that the yellow fever vaccine be administered at 12 months of age. In the case of outbreaks, it can be administered as early as 6 months of age.

Please visit our section Knowledge Resources for Yellow Fever for more information.