Safety of 17D derived yellow fever vaccines

Background: Yellow fever, a mosquito-borne viral haemorrhagic fever, is one of the most lethal viral diseases. At present, an efficient vaccine for prevention is available, but may cause serious adverse events. Methods: The authors review the up-to-date knowledge for serious adverse events of the yellow fever vaccine (YFSAE): hypersensitivity reactions, neurotropic and viscerotropic syndromes. Results: The incidence of YFSAE has been associated with increasing age and thymus disorders, but still a number of cases with any risk factor remain unexplained, which suggests that other factors, from the virus or the host, could be involved in the appearance of these postvaccinal adverse events. Conclusions: YFSAE are uncommon but must be prevented. Further research on the virus-host immune response is needed to have a better understanding of the basis for the appearance of these severe side effects after vaccination. Vaccination should be limited to people with a true risk of exposure to wild-type yellow fever virus.