Quadrivalent influenza HA stem vaccine (SteMos1) with or without ALFQ adjuvant in healthy adults

* INCLUSION CRITERIA:

A participant must meet all of the following criteria:

* Healthy adults between the ages of 18-50 years, inclusive
* Based on history and physical examination, be in good general health and without a history of any of the conditions listed in the exclusion criteria
* Received at least one licensed influenza vaccine from the 2020-2021 influenza season through the 2024-2025 influenza season
* Able and willing to complete the informed consent process
* The ability to read and comprehend English as all consent and recruitment materials are in English.
* Available for clinic visits for 68 weeks after the first dose, including through the 2025-2026 influenza season
* Able to provide proof of identity to the satisfaction of the study clinician completing the enrollment process
* Physical examination and laboratory results without clinically significant findings and a Body Mass Index (BMI) \<= 35 within the 56 days before enrollment
* Agrees to not receive any licensed influenza vaccination during study participation due to potential confounding of study results
* Willing to have blood and mucosal samples collected, stored indefinitely, and used for research purposes.

Laboratory Criteria within 56 days before enrollment:

* WBC and differential within institutional normal range or accompanied by approval of the site Principal Investigator (PI) or designee
* Total lymphocyte count \>= 800 cells/microliter
* Platelets = 125,000-400,000 cells/mircoliter
* Hemoglobin within institutional normal range or accompanied by approval of the PI or designee
* Alanine aminotransferase (ALT) \<= 1.25 x institutional upper limit of normal (ULN)
* Aspartate aminotransferase (AST) \<= 1.25 x institutional ULN
* Alkaline phosphatase (ALP) \< 1.1 x institutional ULN
* Total bilirubin within institutional normal range or accompanied by approval of the PI or designee
* Serum creatinine \<= 1.1 x institutional ULN
* Negative for HIV infection by an FDA-approved method of detection

Criteria applicable to women of childbearing potential:

* Negative beta-human chorionic gonadotropin (beta-HCG) pregnancy test (urine or serum) on the day of enrollment
* Agrees to use an effective means of birth control from at least 21 days prior to enrollment through the end of the study

EXCLUSION CRITERIA:

Participant will be excluded if one or more of the following conditions apply:

-Women who are breast-feeding or planning to become pregnant during the study

A participant has received any of the following substances:

* Receipt of any licensed influenza vaccine or lab-confirmed influenza infection within 6 months prior to enrollment.
* Plan to or are required to receive the 2025-2026 or 2026-2027 licensed influenza vaccines
* Live attenuated vaccines within 4 weeks prior to enrollment
* Inactivated vaccines within 2 weeks prior to enrollment
* mRNA vaccines within 4 weeks prior to enrollment
* Receipt of the HA ferritin influenza vaccine VRC-FLUNPF081-00-VP alone or in prime-boost regimens with VRC-FLUDNA082-00-VP (HA-F A/Sing, DNA A/Sing, VRC 316).
* Receipt of the mosaic quadrivalent influenza vaccine VRC-FLUMOS0111-00-VP (FluMos-v1, VRC 325)
* Receipt of the mosaic hexavalent influenza vaccine VRC-FLUMOS0116-00-VP (FluMos-v2, VRC 326)
* More than 10 days of systemic immunosuppressive medications or cytotoxic medications within the 4 weeks prior to enrollment or any within the 14 days prior to enrollment
* Blood products within 16 weeks prior to enrollment
* Investigational research agents within 4 weeks prior to enrollment or planning to receive investigational products while on the study
* Current allergy treatment with allergen immunotherapy with antigen injections, unless on maintenance schedule
* Current anti-TB prophylaxis or therapy

Participant has a history of any of the following clinically significant conditions:

* Serious reactions to vaccines that preclude receipt of the study vaccinations as determined by the PI or designee
* Hereditary angioedema, acquired angioedema, or idiopathic forms of angioedema
* Asthma that is not well controlled
* Diabetes mellitus (type I or II), except for gestational diabetes
* Thyroid disease that is not well controlled
* Idiopathic urticaria within the past year
* Immune-mediated diseases, such as autoimmune or autoinflammatory diseases, or immunodeficiencies
* Hypertension that is not well controlled
* Bleeding disorder diagnosed by a doctor (e.g., factor deficiency, coagulopathy, or platelet disorder requiring special precautions) or significant bruising or bleeding difficulties with IM injections or blood draws
* Malignancy that is active or history of malignancy that is likely to recur during the period of the study
* Seizure disorder other than 1) febrile seizures, 2) seizures secondary to alcohol withdrawal more than 3 years ago, or 3) seizures that have not required treatment within the last 3 years
* Asplenia, functional asplenia or any condition resulting in the absence or removal of the spleen
* Guillain-Barr(SqrRoot)(Copyright) Syndrome
* Any medical, social condition, occupational reason, or other reason that, in the judgment of the PI or designee, is a contraindication to protocol participation or impairs a participant's ability to give informed consent, including but not limited to clinically significant forms of infectious diseases, drug or alcohol abuse, autoimmune diseases, psychiatric disorders, or heart disease.