Yellow Fever Vaccination As a Model to Study the Response to Stimulation of the Inflammation System

Background: High basal plasma levels of inflammatory molecules are associated with a higher risk of cardiovascular events. It has been suggested that also the dynamic response to an inflammatory trigger is important in determining cardiovascular risk. The aim of the present study was to evaluate the use of vaccination against yellow fever as an in vivo model to study the interindividual variation in the response to inflammatory triggers.

Methods: Ten healthy volunteers were vaccinated with 17D yellow fever vaccine. Blood samples were drawn each day, until Day 8 after vaccination. Automated blood cell counting was performed, and the plasma concentrations of C-reactive protein (CRP), interleukin-6 (IL-6) and fibrinogen were determined.

Results: In most individuals, CRP levels peaked slightly (45% increase from basal values) around Day 7 after vaccination, preceded by an IL-6 (30%) peak around Day 5. Fibrinogen levels showed a significant increase (10%) from Day 2 after vaccination, with a further rise (17%) around Day 5. The monocyte fraction showed a significant 2-fold increase on Day 7 after vaccination. The lymphocyte fraction increased slightly towards Day 7 (not significant).

Conclusion: Our findings show that yellow fever vaccination can be used as a model to study the response to mild stimulation of the inflammatory system.