pH1N1 Blinded Challenge Study

Eligibility Criteria

• 1. Provides signed and dated informed consent form prior to the initiation of any trial procedures.
• 2. Able to understand and agrees to comply with all planned trial procedures and to be available for all study visits.
• 3. Age \>/= 18 and \</= 55 years at time of enrollment.
• 4. Must agree to collection of venous blood and nasal absorption specimens per protocol and enrollment in DMID 19-0025 biorepository protocol for use of residual/repository research blood specimens.
• 5. In good general health.\*
• 6. Able to take oral medication and willing to receive oseltamivir phosphate and/or baloxavir marboxil as part of the study.
• 7. Participants of childbearing potential\* agree to the use of acceptable forms of contraception\*\* for at least 30 days prior to enrollment and agree to use such a method during study participation.
• 8. Non-smoker or non-habitual smoker\* of tobacco, e-cigarettes, or marijuana
• 9. No self-reported or known history of alcoholism within the 2 years prior to enrollment.
• 10. No self-reported or known history of illicit drug use for at least 30 days prior to enrollment.
• 11. Agrees not to use the listed prescription or over the counter medications\* within 7 days prior to confinement and through the confinement period\*\*.
• 12. Screening pulse is 55 to 100 beats per minute, inclusive\*
• 13. Screening systolic blood pressure is 90 to 140 mmHg, inclusive\*
• 14. Screening diastolic blood pressure is 55 to 90 mmHg, inclusive\*
• 15. Screening SpO2 \>/= 95 percent
• 16. Screening respiratory rate is \</= 16
• 17. Screening oral temperature is \<100.4 degrees Fahrenheit
• 18. Screening body mass index (BMI) \>/=18.5 and \<40 kg/m\^2 at screening 19 Screening
• 19. Screening lab test results are within acceptable parameters:\*
• * White blood cell (WBC), Absolute lymphocyte count (ALC), Hemoglobin (Hgb), Platelet (PLT), Alanine transferase (ALT), and Creatinine (Cr).
• * Lab tests within normal range or with grade 1 abnormalities deemed not clinically significant by the site PI or designated clinician licensed to make medical diagnoses and listed on Form FDA 1572 are considered acceptable. Low creatinine and low ALT values are acceptable for trial inclusion as they are not considered to be clinically significant.
• 20. Has a negative test result for hepatitis B surface antigen, hepatitis C virus antibody\*, or HIV types 1 or 2 antibodies at screening.
• 21. Electrocardiogram (ECG) and chest X-ray (CXR) at screening are within normal range or are not deemed clinically significant\*
• 22. Negative respiratory virus panel (including influenza A and B, and SARS-CoV-2) by certified polymerase chain reaction (PCR)-based assay on Day -2 and Day -1.
• 23. Agrees to remain in the confinement unit for at least 6 days after enrollment and until they meet discharge criteria.
• 24. Agrees to adhere to lifestyle considerations during the study. Note: Deviations of lifestyle considerations will be reported as protocol deviations but not as eligibility deviations.
• 1. A history (self-reported or medically documented) of medical or psychiatric condition(s)\* or physical exam finding that precludes participation.
• * Any condition that, in the opinion of the site PI or designated clinician licensed to make medical diagnoses and listed on Form FDA 1572, might interfere with the safety of the participant and/or study objectives including, but not limited to the following:
• * Respiratory disease (e.g., chronic obstructive pulmonary disease \[COPD\], asthma) requiring daily medications (Inhaled, oral, or intravenous corticosteroids, leukotriene modifiers, long and short acting beta agonists, theophylline, ipratropium, biologics) or any treatment for respiratory disease exacerbations (e.g., asthma exacerbation) within the last 5 years
• * Significant cardiovascular disease (e.g., congestive heart failure, cardiomyopathy, ischemic heart disease) or history of myocarditis or pericarditis as an adult
• * Neurological or neurodevelopmental conditions (e.g., epilepsy, stroke, encephalopathy, Guillain-Barre syndrome, encephalomyelitis, or transverse myelitis). A history of febrile seizures during childhood alone is not diagnostic of epilepsy.
• * Anatomic or neurologic abnormality impairing the gag reflex or contributing to aspiration
• * Significant abnormality altering anatomy of nose/nasopharynx (including significant nasal polyps), clinically significant nasal deviation, nasal/sinus surgery within 180 days prior to enrollment, spontaneous epistaxis requiring medical care within 180 days prior to enrollment, chronic or recurrent sinusitis (four or more distinct episodes of sinusitis, with symptom-free intervals between episodes) in the last year prior to enrollment
• * Significant immunodeficiency
• * Known infection by human immunodeficiency virus (HIV) or hepatitis B virus, or known untreated hepatitis C virus infection
• * Ongoing malignancy or diagnosis of malignancy in the last five years (excluding squamous cell or basal cell carcinoma of the skin)
• * Diabetes
• * Blood dyscrasias or significant disorder of coagulation
• 2. HAI antibody titer \>1:40 against influenza A/Arkansas/08/2020 (pH1N1) at screening
• 3. Current or within 4-month use of medications that may be associated with impaired immune responsiveness\* \*Including, but not limited to, immunoglobulin, interferon, immunomodulators, cytotoxic drugs, or systemic corticosteroids (i.e., exceeding 14 days of use and/or exceeding 10 mg/ day prednisone equivalent) or other similar or toxic drugs during the preceding 3-month period prior to screening. Low dose systemic corticosteroids (10mg/day or lower of prednisone) for 14 days or fewer are permitted. Low dose topical and intranasal steroid preparations are allowed, if not within 7 days of challenge or during the confinement period.
• 4. Current pregnancy\* or lactation
• 5. Presence of an internal cardiac device such as a pacemaker or other implanted electronic medical devices
• 6. Has received blood or blood products in the last six months or has plans to donate blood or blood products in the duration of the study
• 7. History of a previous severe allergic reaction to any drug or biologic with generalized urticaria, angioedema, or anaphylaxis
• 8. Allergy or intolerance to treatments for influenza (including any neuraminidase inhibitors or baloxavir marboxil)
• 9. Allergy to two or more classes of antibiotics (e.g., penicillins, cephalosporins, fluoroquinolones, or glycopeptides)
• 10. Allergy to excipients in the challenge virus inoculum
• 11. Presence of any febrile illness or symptoms suggestive of a respiratory infection at the time of enrollment, the time of confinement, or Day 1 pre-challenge
• 12. Close contact with anyone known or suspected to have a respiratory viral illness within 7 days prior to enrollment
• 13. Currently enrolled in any other investigational study or plans to enroll in any other study within the period of this study\*
• 14. Received any live vaccine in the 4 weeks prior to enrollment.
• 15. Received any influenza vaccine in the 4 months prior to enrollment or plans to receive influenza vaccine during the study