The purpose of this pilot research project is to look at the effect of the inactivated influenza vaccine (seasonal flu shot) on early signs of immune or germ-fighting response known as cytokines or signal molecules. The investigators also want to see if the timing of vaccine administration has any effect on women's reproductive hormones. The investigators hypothesis is that influenza vaccine given right before ovulation may change the hormone levels usually seen after ovulation. Thi

This study is an open-label, longitudinal study of healthy young women of reproductive age, not on hormonal contraception who receive seasonal inactivated influenza vaccine (IIV). The women will be followed for one menstrual cycle to measure luteinizing hormone surge, estradiol, and progesterone, and then vaccinated with the seasonal inactivated influenza vaccine prior to ovulation during a second month. At the investigator's discretion, or if there is active circulation of influenza virus in Baltimore, the investigators will vaccinate during the first menstrual cycle (prior to ovulation) and then follow for a second menstrual cycle for comparison. After vaccination, they will be followed for cytokine and chemokine responses as well as changes in the concentrations of steroid hormones. This study will evaluate the effect of IIV on inflammatory cytokines and hormonal responses before and after ovulation. Each woman will have 13 visits in addition to a screening visit, and will be followed for 2 complete menstrual cycles.

Inclusion Criteria:

• Women 18-39 years of age who are in good health.
• Good general health as a result of review of medical history and/or clinical testing at the time of screening.
• Available for the duration of the trial.
• Willingness to participate in the study as evidenced by signing the informed consent document.
• Willing to be abstinent or to use non-hormonal methods of contraception for the duration of the study.
• History of normal menstrual cycles (26-35 days in length) for at least 3 months.
• Willingness to refrain from routine vaccination (except as administered during study) for the duration of the study.

Exclusion Criteria:

• Use of contraceptive pills, patch, injection or other hormonal therapies in the preceding 3 months (6 months for DepoProvera)
• A history of hypersensitivity, including anaphylaxis to any of the components of IIV or to eggs.
• Previous receipt of a same season licensed influenza vaccine.
• Pregnancy as determined by a positive urine or serum human choriogonadotropin (β-hCG) test at any point during the study or in the preceding 3 months.
• Currently is lactating or breast-feeding.
• Fewer than 3 normal menstrual cycles since conclusion of last pregnancy or last use of hormonal birth control.
• A history of autoimmune disease, or any other chronic medical condition considered clinically significant by the investigator.
• History of HIV, Hepatitis C or active Hepatitis B.
• Known immunodeficiency syndrome.
• History of Guillain-Barré syndrome.
• Use of chronic oral or intravenous administration (≥14 days) of immunosuppressive doses of steroids, i.e., prednisone >10 mg per day, immunosuppressants or other immune-modifying drugs within 30 days of starting this study. (Use of topical, nasal or inhaled steroids is permitted)
• Receipt of a live vaccine within 4 weeks or a killed vaccine within 2 weeks prior to study start or during study.
• Receipt of blood or blood-derived products (including immunoglobulin) within 6 months prior to study vaccination.
• Receipt of another investigational vaccine or drug within 30 days prior to study start, or during study.
• Ongoing, daily use of analgesics or anti-inflammatory medications, including nonsteroidal anti-inflammatories. Occasional use, and use associated with menstrual periods is acceptable.

7 days after vaccination, up to 2 months