Response to Influenza Vaccine During Pregnancy

Inclusion Criteria: 1. 18-49-year-old pregnant woman 2. Willing and able to complete the informed consent process 3. Availability for follow-up for the planned duration of the study with the expected delivery date more than 28 days after vaccination 4. Acceptable medical history by review of inclusion/exclusion criteria Exclusion Criteria: 1. Prior off-study vaccination with seasonal influenza vaccine within three months of study vaccination 2. Life-threatening reactions to previous influenza vaccinations 3. Allergy to egg or egg products or to vaccine components including gentamicin, gelatin, or arginine. 4. Active systemic or serious concurrent illness, including febrile illness on the day of vaccination 5. History of immunodeficiency (including HIV infection) 6. Known or suspected impairment of immunologic function; may include significant liver disease, diabetes mellitus treated with insulin or moderate to severe renal disease 7. Chronic Hepatitis B or C. 8. Recent or current use of immunosuppressive medication, including systemic glucocorticoids (corticosteroid nasal sprays and topical steroids are permissible). Use of oral steroids (\<20mg prednisone-equivalent/day) may be acceptable after review by the investigator. 9. Malignancy, other than squamous cell or basal cell skin cancer (includes solid tumors such as breast cancer or prostate cancer with recurrence in the past year, and any hematologic cancer such as leukemia). 10. Autoimmune disease (including rheumatoid arthritis treated with immunosuppressive medication such as Plaquenil, methotrexate, prednisone, Enbrel) which, in the opinion of the investigator might jeopardize volunteer safety or compliance with the protocol. 11. History of blood dyscrasias, renal disease, or hemoglobinopathies requiring regular medical follow up or hospitalization during the preceding year 12. Use of any anti-coagulation medication such as Coumadin or Lovenox, or anti-platelet agents such as aspirin (except up to 325 mg. per day), Plavix, or Aggrenox will be reviewed by investigators to determine if study participation would affect the volunteer's safety or compliance with the protocol. 13. Receipt of blood or blood products within the past 6 months or planned used during the study. 14. A medical or psychiatric condition or occupational responsibilities that preclude participant compliance with the protocol 15. Receipt of an inactivated vaccine 14 days prior to study enrollment, or planned vaccinations prior to completion of last annual study visit (\~ 28 days after study vaccination) 16. Receipt of a live, attenuated vaccine within 60 days prior to enrollment of planned vaccination prior to completion of last study visit (\~ 28 days after study enrollment) 17. Need for allergy immunization (that cannot be postponed) until after the last study visit. 18. History of Guillain-Barre# syndrome 19. Use of investigational agents within 30 days prior to enrollment or planned use during the study. 20. Donation of the equivalent of a unit of blood within 6 weeks prior to enrollment or donation of platelets within 2 weeks of enrollment or planned donation prior to completion of the last visit. 21. Any condition which, in the opinion of the investigator, might interfere with volunteer safety, study objectives or the ability of the participant to understand or comply with the study protocol.