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): 21.0-999.0,  Influenza Healthy males and females 21 to 40 years of age or between 60 and 89, or 90 years or older at the time of enrollment Subjects must provide written informed consent prior to first study intervention Subject is judged to be healthy on the basis of verbal history and physical examination Subject is able to cooperate with the requirements of the study (must be able to complete the diary cards and will be available for 6 months after enrollment) Subject is mentally capable to give consent based on investigator judgment Females of childbearing potential (all women under the age of 40) must agree to use medically approved contraception and must agree to continue using this method for at least three months after enrollment. Females of childbearing potential on hormonal contraception must be stable on hormonal contraception and must agree to use this method of contraception for at least three months after enrollment. Acceptable forms of medically approved contraception the use of: oral contraceptives, injectable contraceptives (i.e., Depo-Provera), transdermal contraceptives or double barrier method All females 40 years of age and under must have a negative urine pregnancy test prior to any vaccination in this trial. Please note that even those participants that have a history of tubal ligation or hysterectomy or are post menopausal (at least one year of no menses) must still have a negative urine pregnancy test prior to any vaccination in this trial Physical examination must be normal, or abnormal findings must be judged not clinically significant for this patient population by the Physician Investigator  Had physician-diagnosed influenza at any time during the past two years Received an influenza vaccine 6 months preceding enrollment in the study Received any other vaccine within 30 days before starting this study or plan to receive any vaccine during the 30 days after enrollment Received immunoglobulin therapy or transfusion with blood or blood products within the previous three months Have known chemical dependency liable to compromise immune function (e.g., alcoholism or illegal drug use not including nicotine or caffeine) Are allergic to eggs or egg products, contact lens solution, or have ever had a severe reaction to any vaccine Have a history of hypersensitivity (allergy) to thimerosal or formaldehyde Have chronic respiratory illnesses (clinically significant and/or on systemic immunosuppressive medications e.g., asthma, COPD, emphysema) Have had symptoms of an active acute respiratory or other active infections or illnesses in the past 72 hours Have a temperature greater than or equal to 100.4 degrees F (38 degrees C) at enrollment