Characterization of Human Memory Immune Responses to Prior Yellow Fever Vaccination

Study Overview
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Brief Summary
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The objective of this study is to study immune memory generated against the yellow fever (YFV) vaccine in participants who have previously received the vaccine. Volunteers will not receive vaccine shots; only immune responses to previous yellow fever vaccination will be studied. The study involves one or multiple blood draws.

Detailed Description
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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

Official Title
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Characterization of Human Memory Immune Responses to Prior Yellow Fever Vaccination

Conditions
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Yellow Fever Vaccine

Participation Criteria
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Eligibility Criteria
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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) Required use of immunosuppressive medications 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

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Group 1: 18 to 45 years of age<br>Between the ages of 18 and 45 at the time of yellow fever vaccination | |
| Group 2: 55 years of age and above<br>Aged 55 or greater at the time of yellow fever vaccination | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Determine the phenotypic and functional characterization of memory T cell responses to YF vaccination | This is an exploratory analysis of variation in immune response with time since last yellow fever virus vaccination. | Immune responses will be measured from at least 30 days after yellow fever vaccination. |