Investigation of Serious Adverse Events Following Vaccination Against Yellow Fever: Emphasis on Genetic Basis and Biological Markers

Inclusion criteria: * Evidence of a systemic reaction in two or more organs within one month of vaccination with yellow fever vaccine; * Laboratory evidence of yellow fever vaccine virus (at least one): Positive culture for more than 7 days after vaccination; RT-PCR ≥ 3 log10 PFU/mL at any day after vaccination; Positive RT-PCR more than 14 days after vaccination; Presence of vaccine virus in tissue by culture, RT-PCR or immunohistochemistry. * Laboratory exclusion of relevant differential diagnosis such as leptospirosis, viral hepatitis and arboviruses. * Cases not obeying these strict criteria but that could be plausibly YEL-AVD or YEL-AND may be included, if approved by the investigator or co-investigators. Exclusion Criteria: * Cases with adverse event after yellow fever vaccine not severe.