Yellow fever is a potentially epidemic arboviral disease, submitted to the international health regulation. The disease is severe but rare in travellers. Immunization protects the individual and prevents transmission to non immune populations. Neurological side effects of the vaccine are rare and already known. More recently severe systemic side effects have been reported, with a seemingly age increasing incidence (1,8/100,000 in the over 60 years old). They seem related to host immunity rather than to an increased virulence of the vaccines. The indication and contra indications to the vaccine must be followed strictly according to the benefit/side effects ratio and to the epidemiology.