Yellow fever vaccine prevents against Yellow Fever, a viral hemorrhagic disease caused by the transmission of a flavivirus through the bite of an infected mosquito. Symptoms of Yellow fever can range from asymptomatic, to mild flu-like illness, to more severe symptoms such as shock, jaundice, internal bleeding, and organ failure . Interestingly, Yellow fever got its name from the characteristic yellowing of the skin and eyes that occurs from the development of jaundice when the virus attacks the liver. Although there is supportive treatment available for managing Yellow Fever, there are currently no antivirals developed to specifically treat Yellow Fever. Vaccination with Yellow Fever vaccine is therefore considered to be the most important and effective measure to protect against Yellow Fever, with protective immunity developing within 10 days after vaccination; in two separate clinical trials of Yellow Fever Vaccine, 90% of subjects seroconverted within 10 days after vaccination, and 100% of subjects seroconverted within 14 days . The World Health Organization no longer recommends the use of a 10-year booster dose following primary immunization, as a single dose is "sufficient to confer life-long immunity against yellow fever disease" . Yellow Fever is most commonly found in the southern hemisphere, in tropical regions of Africa and Central/South America . The World Health Organization recommends routine vaccination in countries where Yellow Fever is endemic, and for travellers going to endemic areas as proof of vaccination is often a requirement at border crossings to prevent international spread of the disease . Yellow Fever Vaccine is a subcutaneously administered vaccination for the active immunization and prophylaxis of yellow fever in pediatric patients 9 months of age and older. It is composed of two live, attenuated strains of yellow fever virus, 17D-204 and 17DD, which have been shown to elicit an immune response identical to that induced by wild-type infection . The FDA recommends vaccination with Yellow Fever Vaccine for persons living in or travelling to endemic areas and for laboratory personnel who handle virulent yellow fever virus or concentrated preparations of the yellow fever vaccine virus.