Patient description: A 42-year-old healthy woman came to the clinic to have her flu shot in early October. She works in a rehab center and has no underlying disease. It's her first time getting the vaccine this year. She is married for 5 years and uses barrier methods of contraception. Her menstrual cycle is irregular. She does not smoke. She is not on any medications. She exercises regularly for 30 minutes a day at least 5 days a week. She has no history of allergies to any food or drugs. Her past surgical history is significant for tonsillectomy and she is otherwise healthy.

Clinical trial eligibility criteria: eligible ages (years): 21.0-49.0,  Influenza Subject is between the ages of 21 to 49 years of age on day of enrollment, visit 1(day 0). 2. Provides written informed consent. 3. Subject is judged to be healthy on the basis of verbal medical and concomitant medications history and has been medically stable prior to screening 4. Subject is able to attend scheduled visits and to comply with the study procedures during the entire duration of the study and will be available for 1 month after enrollment. 5. Female is not at risk of pregnancy, based on the following: 1. Utilizing adequate method of birth control and agree to continue using this method for at least 1 month after enrollment. Adequate methods of birth control may hormonal (oral, transdermal, or injectable) or double barrier methods (eg condom with spermicide, vaginal combined ring) or intra-uterine device. If using hormonal method or intra-uterine device, usage should be stable for 1 month prior to vaccination and should continue for 1 month post vaccination. 2. Negative urine pregnancy test is required for all females at study entry. Females surgically sterilized (history of tubal ligation or total or subtotal hysterectomy) or post-menopausal for 2 years must still have a negative pregnancy test at time of enrollment. 6. Subject should be available through telephone contact and agree to participate in all scheduled visits  Adults younger than 21 years of age or 50 years and older 2. Subject had physician-diagnosed (preferably by culture) influenza at any time during the past 2 years. 3. Subject received an influenza vaccine in the 6 months preceding enrollment in the study 4. Subjects who receive any live virus vaccine within one month of enrollment and any inactivated or subunit vaccine within 2 weeks of enrollment or with plans to receive any vaccine during this study will be excluded from the study, eg, pneumococcal vaccine. 5. Subject received blood or blood products in the last 3 months. 6. Subject has asthma or reactive airway disease. 7. Subject has a history of any serious vaccine reactions or anaphylaxis or reactions likely to be exacerbated by any component of the study vaccine, 8. Subject is allergic to eggs, egg products or gentamycin. 9. Subject has known or suspected disease(s) of the immune system with immunosuppression, eg, rheumatoid arthritis, systemic lupus erythematosus (SLE), lymphoma, human immunodeficiency virus (HIV), cancer diagnoses or treatment within the last 5 years (except skin cancer), etc. 10. Subject is currently being treated with an immunosuppressive medications (ie, cancer therapeutic agents such as tamoxifen, systemic corticosteroids such as prednisone, and arthritis medications such as methotrexate). Please note that inhaled or topical corticosteriods are acceptable. 11. FluMist recipients in close contact (eg, within the same household) with immunocompromised individuals during periods in which the immunosuppressed person requires care in a protective environment. (contact should be avoided for at least 21 days). Contact with small children is not an exclusion. Females who breastfeed are excluded. 12. Drug interactions: On antiviral therapy in 48 hours preceding scheduled vaccination 13. Antiviral agents administered until 3 weeks after FluMist vaccination. 14. Participation in any other interventional drug or vaccine trial within 30 days prior to enrollment. Therefore subject is not to receive other investigational products (drug or vaccine) during the length of their participation in the trial. 15. Subject has acute respiratory illness. Administration of FluMist should be postponed until after the acute phase (at least 72 hours) of respiratory illnesses. 16. Subject has active infections or illnesses. 17. Subject had an acute illness with or without fever (temperature >/= 99.5 F [oral]) in the 72 hours preceding vaccination. Administration of FluMist should be postponed until after the acute phase (at least 72 hours) of febrile and/or acute illnesses. 18. Subject has acute or chronic medical health condition that, in the opinion of the investigator, would render vaccination unsafe or would interfere with the evaluation of responses. These conditions but are not limited to health problems associated with 1. heart disease, (if heart failure is present, New York Heart Association Functional Class III or IV), 2. kidney disease, (history of significant renal impairment e.g., dialysis and treatment for kidney disease, including diabetic and hypertensive kidney disease), 3. chronic liver disorders (e.g. hepatitis B or C), 4. diabetes mellitus (excluding diet-controlled diabetes), 5. arteriosclerotic event during the 6 months prior to enrollment (eg, history of myocardial infarction, stroke, recanalization of femoral arteries, or transient ischemic attack), 6. functional or anatomic asplenia, 7. cancer diagnosed and treated within the past 5 years with chemotherapy, radiation therapy and/or surgery 8. significant anemia or other blood disorders. 9. Underlying unstable chronic disease e.g.uncontrolled hypertension (systolic blood pressure >180 mm Hg or diastolic blood pressure >100 mm Hg at Visit 1), etc. 19. Subject has any active neurologic disorders (ie, encephalopathy, optic neuritis/neuropathy, partial facial paralysis, and brachial plexus neuropathy). 20. Subject is pregnant or planning to become pregnant within the next 2 months. 21. Subject is breastfeeding. 22. Subject has any condition that would, in the opinion of the site investigator, place the subject at an unacceptable risk of injury or render the subject unable to meet the requirements of the protocol. 23. Subject has a prior history of Guillain-Barré syndrome. 24. Subject has a history of drug or alcohol abuse