Could a booster make your flu shot work better? new study investigates

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: 1. Provide written informed consent prior to initiation of any study procedures. 2. Are able to understand and comply with planned study procedures and be available for all study visits. 3. Must agree to the collection of venous blood per protocol. 4. Are males or non-pregnant females, 18 to 45 years of age, inclusive at time of enrollment. 5. Are in good health\*. \*As determined by medical history and physical examination to evaluate acute or currently ongoing chronic medical or psychiatric diagnoses or conditions, defined as those that have been present for at least 90 days, which would affect the assessment of the safety of subjects or the immunogenicity of study vaccinations. Chronic medical diagnoses or conditions should be stable for the last 60 days (no hospitalizations, emergency room or urgent care for condition, or invasive medical procedure and no adverse symptoms that need medical intervention such as medication change/supplemental oxygen). This includes no change in chronic prescription medication, dose or in the 60 days prior to enrollment. Any prescription change that is due to change of health care provider, insurance company, etc., or that is done for financial reasons, as long as in the same class of medication, will not be considered a deviation of this inclusion criterion. Subjects may be on chronic or as needed (prn) medications if, in the opinion of the site PI or appropriate sub-investigator, they pose no additional risk to subject safety or assessment of reactogenicity and immunogenicity and do not indicate a worsening or treatment of continued symptoms of medical diagnosis or condition. Note: Low dose topical, corticosteroids as outlined in the Subject Exclusion Criteria as well as herbals, vitamins and supplements are permitted. 6. Oral temperature is less than 100.0 degrees Fahrenheit. 7. Pulse is 47 to 100 beats per minute, inclusive. 8. Systolic blood pressure is 85 to 140 mmHg, inclusive. 9. Diastolic blood pressure is 55 to 90 mmHg, inclusive. 10. Screening laboratories (Erythrocyte Sedimentation Rate (ESR), White Blood Cells (WBC), Hemoglobin (Hgb), Platelets (PLTs), Alanine Aminotransferase (ALT), Total Bilirubin (T. Bili), Aspartate Aminotransferase (AST), Gamma-glutamyl Transferase (GGT), Alkaline Phosphatase (ALP) serum lipase, serum amylase and Creatinine (Cr)) are within acceptable parameters\*. \*ESR must be below 30 mm/hr; WBC \>3.90 K/MM3 and \<10.60 K/MM3; Hgb \>/= 11.5 g/dl (women) or \>/= 12.5 g/dl (men); PLTs (EDTA) 140-415 K/MM3; PLTs (Citrate) 125-325 K/MM3 ALT \</= 43 U/L (women) or \</= 60 U/L (men); T Bili \</=1.20 mg/dl; Cr \< 1.1 mg/dl (women) or \< 1.4 mg/dl (men); AST 10-36 U/L (women) or 10-43 U/L (men); GGT 5--32 U/L (women) or 10-49 U/L (men); ALP 30-115 U/L (women) or 43-115 U/L (men); lipase 13-60 U/L; amylase (Total) 35-121 U/L, for subjects to qualify for randomization and vaccination. 11. Women of childbearing potential\* must use an acceptable contraception method\*\* from at least 30 days before the first study vaccination until 60 days after the second study vaccination. \*Not sterilized via bilateral oophorectomy, tubal ligation/ salpingectomy, hysterectomy, or successful Essure(R) placement (permanent, non-surgical, non-hormonal sterilization) with documented radiological confirmation test at least 90 days after the procedure, and still menstruating or \<1 year has passed since the last menses if menopausal. * Includes non-male sexual relationships, full abstinence from sexual intercourse with a male partner, monogamous relationship with vasectomized partner who has been vasectomized for 180 days or more and shown to be azoospermic prior to the subject receiving the study vaccination, barrier methods such as condoms or diaphragms/cervical cap with spermicide, effective intrauterine devices, NuvaRing(R), and licensed hormonal methods such as implants, injectables or oral contraceptives ("the pill"). 12. Women of childbearing potential must have a negative urine or serum pregnancy test within 24 hours prior to the first study vaccination. 13. For a woman with potential to become pregnant, she understands that in the event of pregnancy during the study she will be approached to enroll in the Sanofi Pregnancy Registry. 14. Must agree to have residual specimens (i.e. residual/excess of per protocol specifications). Exclusion Criteria: 1. Have an acute illness\*, as determined by the site Principal Investigator (PI) or appropriate sub-investigator, within 72 hours prior to study vaccination. \*An acute illness which is nearly resolved with only minor residual symptoms remaining is allowable if, in the opinion of the site PI or appropriate sub-investigator, the residual symptoms will not interfere with the ability to assess safety parameters as required by the protocol. 2. Have any medical disease or condition that, in the opinion of the site PI or appropriate sub-investigator, is a contraindication to study participation\*. \*Including acute, subacute, intermittent or chronic medical disease or condition that would place the subject at an unacceptable risk of injury, render the subject unable to meet the requirements of the protocol, or may interfere with the evaluation of responses or the subject's successful completion of this trial. 3. Have immunosuppression as a result of an underlying illness or treatment, a recent history or current use of immunosuppressive or immunomodulating disease therapy. 4. Use of anticancer chemotherapy or radiation therapy (cytotoxic) within 3 years prior to study vaccination. 5. Have known active or recently active (12 months) neoplastic disease or a history of any hematologic malignancy. Non-melanoma, treated, skin cancers are permitted. 6. Have known human immunodeficiency virus (HIV), hepatitis B or hepatitis C infection. 7. Have known hypersensitivity or allergy to eggs, egg or chicken protein, squalene-based adjuvants, or other components of the study vaccine. 8. Have a history of severe reactions following previous immunization with licensed or unlicensed influenza vaccines. 9. Have a history of Guillain-Barré Syndrome (GBS). 10. Have a history of convulsions or encephalomyelitis within 90 days prior to study vaccination. 11. Have a history of Potentially Immune-Mediated Medical Conditions (PIMMCs). 12. Have a history of alcohol or drug abuse within 5 years prior to study vaccination. 13. Have any diagnosis, current or past, of schizophrenia, bipolar disease or other psychiatric diagnosis that may interfere\* with subject compliance or safety evaluations. \*As determined by the site PI or appropriate sub-investigator. 14. Have been hospitalized for psychiatric illness, history of suicide attempt, or confinement for danger to self or others within 5 years prior to study vaccination. 15. Have taken oral or parenteral (including intra-articular) corticosteroids of any dose within 30 days prior to study vaccination. 16. Have taken high-dose inhaled corticosteroids\* within 30 days prior to study vaccination. \*High-dose defined as per age as using inhaled high-dose per reference chart in the National Heart, Lung and Blood Institute Guidelines for the Diagnosis and Management of Asthma (EPR-3) or other lists published in UPTODATE. 17. Received or plan to receive a licensed, live vaccine (excluding all licensed, seasonal LAIVs) within 30 days before or after the study vaccination. 18. Received or plan to receive a licensed, inactivated vaccine (excluding all licensed, seasonal IIVs) within 14 days before or after each study vaccination. 19. Have received any 2018/2019 seasonal influenza vaccine within the 6 months prior to enrollment. 20. Plans to receive any 2019/2020 seasonal influenza vaccine within approximately 90 days of receipt of the first study vaccination. 21. Have a known history of documented influenza infection within the past 6 months. 22. Received immunoglobulin or other blood products (except Rho D immunoglobulin) within 90 days prior to study vaccination. 23. Received an experimental agent\* within 30 days prior to the study vaccination or expect to receive another experimental agent\* during the trial-reporting period\*. \*Including vaccine, drug, biologic, device, blood product, or medication. \*\*Other than from participation in this trial. \*\*\*Approximately 12 months after the first study vaccination. 24. Are participating or plan to participate in another clinical trial with an interventional agent\* that will be received during the trial-reporting period\*\*. \*Including licensed or unlicensed vaccine, drug, biologic, device, blood product, or medication. \*\*Approximately 12 months after the first study vaccination. 25. Female subjects who are breastfeeding or plan to breastfeed from the time of the first study vaccination through 30 days after the last study vaccination. 26. Plan to travel outside the US (continental US, Hawaii and Alaska) from the time of study vaccination through approximately 90 days after the first study vaccination. 27. Planning to donate blood within 4 months following first vaccination. Exclusion Criteria for Second Study Vaccination: All study participants will be expected to receive the second study vaccination except under the circumstances listed below. The second study vaccination will not be administered to a subject if any of the following criteria are met: * Meets the contraindication on the package insert to receipt of licensed influenza vaccine. * As deemed necessary by the site principal investigator or appropriate sub-investigator for noncompliance or other reasons. * Subject refusal of further study vaccination. * Withdrawal of consent. * Subject is lost to follow-up. * Termination of this trial. * New information becomes available that makes further participation unsafe.