Characterization of Humoral and Cellular Immune Responses Elicited by Influenza Vaccination in Healthy Adults

This study examines how the immune system responds to the annual influenza (flu) vaccine in healthy adults. Researchers will collect blood samples before and after vaccination to measure antibody levels and immune cell activity, aiming to understand what makes some people respond to the vaccine better than others. You may be eligible if: • You are 18 years of age or older • You are in good health based on a self-reported health survey • You are willing and able to attend all study visits You may NOT be eligible if: • You have a known allergy to the flu vaccine ingredients or latex • You have had a severe reaction to a previous flu vaccine • You have a history of Guillain-Barré syndrome within 6 weeks of receiving a flu vaccine • You are immunosuppressed due to illness or treatment (including chemotherapy in the past 36 months) • You are pregnant • You have known HIV, hepatitis B, or hepatitis C infection • You have received an influenza vaccine in the past 2 months • You received immunoglobulin or a blood product in the past 3 months • You have active cancer currently being treated • You are currently taking long-term steroids Talk to your doctor to see if this trial is right for you.