Immune Responses to Yellow Fever Vaccine

The goal of this study is to characterize immune memory in humans who have previously
received yellow fever vaccine. The project is designed to study the magnitude and persistence
of both humoral, and cell-mediated immune memory generated post-vaccination. Since aging has
an effect on the immune system (eg. decreased thymic output, replacement of hematopoietic
cells in the bone marrow with adipocytes), the researchers will analyze the young adults
(aged 18-45 years) and the older vaccinees (55 years or older) in separate groups.

The specific aims of the study are to:

- Determine the phenotypic and functional characterization of memory T cell responses to
yellow fever vaccination

- Determine neutralizing antibody titer after yellow fever vaccination

Inclusion Criteria:

- Able to understand and give informed consent

- Age 18-45 years (Group 1) or 55 years and above (Group 2) at the time of yellow fever
vaccination

- Documentation (international certificate of vaccination (yellow card) or medical
record) indicating receipt of yellow fever vaccine.

Exclusion Criteria:

- Recipient of any vaccines within 30 days before the study visit (not applicable to
older adults)

- History of a progressive and severe chronic medical condition resulting in impaired
immunity (such as diabetes, kidney or liver dysfunction)

- Reporting HIV, Hepatitis B (surface antigen positive) or Hepatitis C infections
(antibody positive) on the medical/health history form

- Recipient of a blood product or immune globulin product within 42 days of study visit

- Reporting pregnancy