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): 18.0-999.0,  Influenza Subjects who the investigator believes can and will comply with the requirements of the protocol Written informed consent obtained from the subject Male and female adults, >= 18 years of age at the time of the first vaccination Safety laboratory test results within the parameters specified in the protocol Satisfactory baseline medical assessment by history and physical examination Comprehension of the study requirements, ability to comprehend and comply with procedures for collection of safety data, expressed availability for the required study period, and ability and willingness to attend scheduled visits as documented by signature on the informed consent document Access to a consistent means of telephone contact, which may be either in the home or at the workplace, land line or mobile, but NOT a pay phone or other multiple-user device Female subjects of non-childbearing potential may be enrolled in the study Female subjects of childbearing potential may be enrolled in the study, if the subject has practiced adequate contraception for 30 days prior to vaccination, and  Medical history of physician-confirmed infection with an A/California/7/2009 (H1N1)v-like virus Previous vaccination at any time with an H1N1v-like virus vaccine or a medical history of physician-confirmed infection with an H1N1v-like virus Presence of evidence of substance abuse or of neurological or psychiatric diagnoses which, even if stable, are deemed by the investigator to render the potential subject unable/unlikely to provide accurate safety reports Presence of a temperature >= 38.0ºC (>=100.4ºF), or acute symptoms greater than "mild" severity on the scheduled date of first vaccination Diagnosed with cancer, or treatment for cancer, within 3 years Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination (no laboratory testing required) Receipt of systemic glucocorticoids within 1 month prior to study enrollment, or any other cytotoxic or immunosuppressive drug within 6 months of study enrollment. Topical, intra-articularly injected, or inhaled glucocorticoids, topical calcineurin inhibitors or imiquimod are allowed Receipt of any immunoglobulins and/or any blood products within 3 months of study enrollment or planned administration of any of these products during the study period Any significant disorder of coagulation or treatment with warfarin derivatives or heparin. Persons receiving individual doses of low molecular weight heparin outside of 24 hours prior to vaccination, are eligible. Persons receiving prophylactic antiplatelet medications, e.g., low-dose acetylsalicylic acid, and without a clinically-apparent bleeding tendency, are eligible An acute evolving neurological disorder or history of Guillain-Barré syndrome within 6 weeks of receipt of seasonal influenza vaccine