Influenza Vaccine Response

The goal of this clinical trial is to measure the immune response in the blood, nose, and lungs after participants receive either the FDA-approved inactivated influenza vaccine or the FDA-approved intranasal FluMist vaccine. The study will evaluate immune responses in groups of healthy, non-pregnant, volunteers between the ages of 18 and 40. The main purpose of the study is to measure the change in influenza vaccine-specific antibodies in the lower lungs and nose between vaccination and 14 days after participants receive the vaccine. All participants will be randomized to receive one of the two seasonal flu vaccines and will have blood and back of the nose swabs collected throughout the study. Some study participants will choose to undergo optional bronchoscopy procedures and will be included in the part of the study looking at lower lung immune responses.

The aim of this clinical trial is to explore the efficacy of fatty acid and bile acid based supplements on enhancing influenza vaccine immune response in adults aged 60-70 years. The objectives of this study are: 1. To explore the efficacy of fatty acid and bile acid based supplements on enhancing flu vaccine immune response. 2. To evaluate the safety of fatty acid and bile acid use in elders. 3. To explore the potential role of microbiota in regulating immune response. This study will conduct a randomized clinical trial to compare the efficacy of fatty acid / bile acid (Tauro Ursodesoxy Cholic Acid, TUDCA)supplements on enhancing vaccine immune response. The antibody's titer and safety indicators after influenza vaccination will be evaluated. Study process are: 1. Participants will be required to intake the assigned supplement or placebo daily for 25 days; 2. Receive a influenza vaccine on day 4; 3. Provide blood samples three times and stool samples twice at base line and endpoint respectively; 4. The antibody's titer and safety indicators will be analyzed and compared among groups. This study aims to establish a theoretical foundation for utilizing nutritional strategies to enhance vaccine-induced immune responses and to provide a scientific framework for developing oral vaccine boosters.