Yellow fever vaccine
Yellow fever (YF) virus infection causes a systemic infection including fever, headache, vomiting, and muscle pains and may evolve into a full hemorrhagic fever syndrome. Infection occurs from day-biting mosquitoes in tropical South America and sub-Saharan Africa. YF vaccine is given either for personal protection against YF disease or may be required for entry into a country (or for both reasons). One dose of live virus vaccine is given and becomes effective in about 10 days, protecting for at least 10 years. A booster dose may be needed every 10 years for some travelers. Rarely, severe reactions with multi-organ failure or encephalitis can occur.