The Effect of Inflammation and Damage to Lymph Node Structures on Durable Protective Immunity Following Yellow Fever Vaccination

Inclusion Criteria: * No contraindication to Yellow Fever vaccine (immunosuppressed for any reason or on an immunosuppressive drug where a live virus vaccine is contraindicated). * If female of childbearing age must agree to contraception for one month following administration of the vaccination. Exclusion Criteria: * History of yellow fever or previous vaccination for yellow fever * Known bleeding disorder * Prior surgery complicated by clotting abnormality * Psychiatric or behavioral disorder that, in the opinion of the investigator, will make it difficult for the participant to complete the study * History of acute hypersensitivity reaction to any component of the vaccine (including gelatin, eggs, egg products, or chicken protein). * Thymus disorder associated with abnormal immune function * Immunosuppression from any of the following: HIV infection or AIDS, malignant neoplasms, primary immunodeficiencies, transplantation, transplantation, immunosuppressive or immunomodulatory therapy (corticosteroids, alkylating agents, antimetabolites, TNF inhibitors, IL-1 blocking agents, monoclonal antibodies targeting immune cells), previous radiation therapy. * Pregnant or breastfeeding at the time of vaccination. * Planning to conceive within 28 days of enrollment and vaccination with the yellow fever vaccine.