Yellow Fever
Yellow fever vaccine, a single-dose attenuated live virus vaccine prepared in eggs, should be given at least 10 days before travel to endemic areas, which include much of tropical South America and sub- Saharan Africa between 15°N and 15°S. Some countries in Africa require an International Certificate of Vaccination against yellow fever from all entering travelers; other countries in Africa, South America and Asia require evidence of vaccination from travelers coming from or traveling through endemic or infected areas. The vaccine is available in the US only at centers certified by state health department. Boosters are given every 10 years, but immunity probably lasts much longer.