Evaluating the Dose, Safety, Tolerability, and Immunogenicity of Mosaic Hexavalent Influenza Vaccine VRCFLUMOS0116-00-VP (FluMos-v2) With and Without ALFQ Adjuvant in Healthy Adults

Eligibility 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 2023-2024 influenza season
• * Able and willing to complete the informed consent process
• * Available for clinic visits for 68 weeks after enrollment, 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 the 2025-2026 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
• * White blood cells (WBC) and differential within institutional normal range or accompanied by approval of the site Principal Investigator (PI) or designee
• * Total lymphocyte count \>= 800 cells/microL
• * Platelets = 125,000 - 400,000 cells/microL
• * 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 method of birth control from at least 21 days prior to enrollment through the end of the study.
• * A participant will be excluded if one or more of the following conditions apply:
• * A Participant has received any of the following substances:
• * Receipt of any licensed influenza vaccine within 6 months prior to enrollment.
• * Plan to or are required to receive the 2025-2026 or received the 2024-2025 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 20 mcg of the influenza vaccine VRC-FLUNPF081-00-VP (HA-F A/Sing, VRC 316, Group 1)
• * 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-Barre 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.