Inclusion Criteria:
* Can understand and comply with all planned study procedures.
* Healthy, non-pregnant, non-breast-feeding persons aged ≥18 and ≤49 years of age inclusive at the time of challenge.
* Persons biologically able to become pregnant must be practicing abstinence or using an acceptable method of birth control for at least 30 days before the challenge through the duration of the trial. Persons biologically able to make someone pregnant must agree not to get their partner pregnant for the duration of the trial.
* A person is considered of childbearing potential unless post-menopausal (absence of menses for ≥1 year) or surgically sterilized (tubal ligation/salpingectomy, bilateral oophorectomy, or hysterectomy).
* Acceptable contraception methods for persons of childbearing potential include but are not limited to: sexual abstinence from intercourse with partners biologically able to make them pregnant, monogamous relationship with a vasectomized partner, barrier methods such as condoms or diaphragms with spermicide or foam, effective devices (IUDs, NuvaRing®) or licensed hormonal products such as implants, injectables or oral contraceptives.
* Persons of childbearing potential must have a negative serum or urine pregnancy test at screening and a negative urine pregnancy test within 24 hours before challenge.
* Are in good general health, as determined by the study investigator within 30 days of challenge, and do not have any of the following conditions:
* Chronic pulmonary disease (e.g., asthma or emphysema).
* Chronic cardiovascular disease (e.g., cardiomyopathy, congestive heart failure, cardiac surgery, ischemic heart disease, known anatomic defects).
* Chronic medical conditions requiring close medical follow-up or hospitalization during the past 5 years (e.g., diabetes mellitus, renal dysfunction, hemoglobinopathies).
* Immunosuppression, ongoing malignancy, or history of malignancy (excluding non-melanotic skin cancer in remission without treatment for more than 5 years).
* Neurological and neurodevelopmental conditions (e.g., cerebral palsy, epilepsy, stroke, seizures).
* History of postinfectious or postvaccine neurological sequelae.
* Autoimmune, inflammatory, vasculitis, or rheumatic disease, including but not limited to systemic lupus erythematosus, polymyalgia rheumatica, rheumatoid arthritis, or scleroderma.
* Demonstrate knowledge and comprehension of the study by scoring ≥70% on a quiz on the study protocol and policies.
* Agrees to not use cigarettes, e-cigarettes, marijuana, or other tobacco products during the quarantine period.
* Agrees not to use prescription or over-the-counter medications that could impact influenza challenge efficacy or symptoms (including oseltamivir, zanamivir, peramivir, baloxavir marboxil, amantadine and rimantadine, aspirin, intranasal steroids, acetaminophen, decongestants, antihistamines, and other NSAIDs), within 14 days before challenge and through the quarantine period, unless approved by the investigator.
Exclusion Criteria:
* Have household contact with or have daily contact with:
* Children under 5 years of age.
* Children and/or teenagers who are receiving long-term aspirin therapy.
* Persons who are pregnant or who are trying to become pregnant.
* Persons older than 65 years of age.
* Persons of any age with significant chronic medical conditions such as:
* Chronic pulmonary disease (e.g., asthma, emphysema, COPD).
* Chronic cardiovascular disease (e.g., cardiomyopathy, congestive heart failure, cardiac surgery, ischemic heart disease, known anatomic defects).
* Contacts who required medical follow-up or hospitalization during the past 5 years because of chronic metabolic disease (e.g., diabetes mellitus, renal dysfunction, hemoglobinopathies).
* Immunosuppression or cancer.
* Neurological and neurodevelopmental conditions (e.g., cerebral palsy, epilepsy, stroke, seizures).
* Healthcare workers with patient contact during the two weeks following the influenza challenge.
* Plan to live in a confined environment (e.g., ship, camp, or dormitory) during the two weeks following the influenza challenge.
* Pregnant persons or are planning to become pregnant at any time during the study.
* Persons who are breastfeeding or plan to breastfeed at any time during the study.
* Have a body mass index (BMI) less than or equal to 18.5 or greater than or equal to 35.
* Smoke more than four cigarettes, e-cigarettes, marijuana, or other tobacco products weekly within 60 days before the challenge.
* Have moderate or severe illness within seven days before the challenge. This includes but is not limited to an oral temperature of ≥100°F, diarrhea, or vomiting.
* Have a pulse rate of less than 55 beats per minute (bpm) or greater than 100 bpm (participants will not be excluded if the heart rate is 55 bpm with moderate exercise (e.g., walking up two flights of stairs))
* Have a systolic blood pressure of less than 90 mmHg or greater than 140 mmHg on two separate measurements (screening and pre-challenge).
* Have a diastolic blood pressure of less than 50 mmHg or greater than 90 mmHg on two separate measurements (screening and pre-challenge).
* Have long-term (≥2 weeks) use of high-dose oral (≥20 mg per day prednisone or equivalent) or parenteral glucocorticoids, or high-dose inhaled steroids for greater than 7 days in the last 3 months.
* Have an active HIV, hepatitis B, or hepatitis C infection.
* Have screening laboratory test results (white blood cells \[WBC\], absolute neutrophil count \[ANC\], hemoglobin, platelets) that are outside the laboratory reported normal values and deemed clinically significant by the study investigator.
* Have a serum creatinine greater than 1.1 x upper limit of normal (ULN).
* Have an alanine aminotransferase (ALT) greater than 1.1 x ULN.
* Have abnormal findings on screening electrocardiogram deemed clinically significant by the study investigator.
* Have abnormal findings on screening chest X-ray deemed clinically significant by the study investigator.
* Have ongoing drug or alcohol abuse and/or dependence within five years of challenge.
* Have positive urine/serum test for drugs of abuse (i.e. cocaine, benzodiazepines, opiates, or metabolites).
Positive results for tetrahydrocannabinol (THC) will not be considered exclusionary. Metabolites and amphetamines as prescribed for a documented medical condition will also not be considered exclusionary.
* Have any medical, psychiatric, occupational, or behavioral problems that could make it difficult for the participant to comply with the protocol as determined by the investigator.
* Have received experimental products within 30 days before the challenge or plan to receive experimental products at any time during the study.
* Plan to enroll in another clinical trial that could interfere with the safety assessment of the investigational product at any time during the study period, including study interventions such as drugs, biologics, or devices.
* Plan to donate blood during the study.
* Have received a live vaccine within 30 days before the challenge or plan to receive a live vaccine before Day 31 post-challenge.
* Have received an inactivated vaccine within 14 days before the challenge or plan to receive an inactivated vaccine before Day 14 of the challenge.
