Study on How Long Protection Lasts After Yellow Fever or Influenza Vaccination

What this Trial Is About

The trial investigates the differences in immune protection duration provided by two vaccines the yellow fever vaccine YF-17D and the quadrivalent influenza vaccine QIV. The yellow fever vaccine is known for long-lasting immunity after a single dose, while the influenza vaccines protection fades quickly. The study aims to better understand the immune signals that lead to durable protection, which are currently not well known, by comparing immune responses to these vaccines. Participants will receive either the FDA-approved yellow fever vaccine or the quadrivalent influenza vaccine. After vaccination, biological samples will be collected from the blood, lymph nodes, and bone marrow at baseline and follow-up visits. Lymph node sampling involves fine needle aspirates or core biopsies performed up to twice, and bone marrow aspirates up to three times per participant. Vaccination visits include observation for immediate reactions, and participants receive documentation of vaccination when applicable. During the study, participants will undergo screening with informed consent and eligibility assessment, vaccination, tissue sampling procedures, and several follow-up visits. Assessments include medical history, vital signs, pregnancy tests for those able to become pregnant, and HIV testing at screening. Researchers will monitor immune responses over time by analyzing the collected samples. Safety is tracked through reported adverse events. The study is expected to continue through September 2027, with follow-up lasting up to 270 days after vaccination.

Durability of Vaccine Responses