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.