Durability of Vaccine Responses

The ability of the vaccines today to generate a long-lasting protection against infections varies greatly from one vaccine to another. The yellow fever vaccine (YF-17D) is one of the most successful vaccines ever developed, having been administered to over 600 million people globally. A single vaccination is known to induce durable protection over several decades. In contrast, the quadrivalent influenza vaccine (QIV) generates an immunity that wanes quickly with no long-lasting protection. Currently, the duration of immune protection for new vaccines is difficult to predict during vaccine product development and can only be ascertained by a "wait and see" approach. This is due, in part, to the fact that some of the signals that activate a durable immune system protection remain unknown. This study aims to provide a better understanding of this problem by vaccinating willing participants with either the FDA-approved yellow fever vaccine or the quadrivalent influenza vaccine and collecting baseline and follow-up biologic samples to compare how the immune system reacts.

NCT Number	NCT05801978
Lead Sponsor	Emory University Collaborators: Defense Advanced Research Projects Agency, Open Philanthropy
Conditions	Vaccine Response
Enrollment	66 participants
Start Date	2023-04-11
Primary Completion	2027-09 (estimated)
Study Completion	2027-09 (estimated)
Updated on ClinicalTrials.gov	2026-07-17