A Clinical Study to Evaluate the Safety, Tolerability, and Immunogenicity of VAX-A1 in Healthy Young Adults

Inclusion Criteria:

• Individuals 18-40 years of age (inclusive) at the time of randomization into the study
• Able and willing to complete the informed consent process
• Available for clinical follow-up through the last study visit at 6 months post-Dose 2
• Willing to have blood samples collected, stored indefinitely, and be used for research purposes
• Able to provide proof of identity to the satisfaction of the study staff completing the enrollment process
• Healthy, as defined by absence of clinically significant medical condition, either acute or chronic, as determined by medical history, vital signs, physical examination, screening laboratory test results, TTE and ECG results, and clinical assessment by the Investigator
• For applicable individuals, postmenopausal (as confirmed by follicle-stimulating hormone [FSH] level at Screening) for at least 1 year, or surgically sterile for at least 6 months prior to dosing
• Individuals of childbearing potential must be not pregnant and not lactating, must have negative urine and serum pregnancy tests at Screening and a negative urine pregnancy test immediately prior to randomization, and agree to use acceptable contraception if heterosexually active. Participants must agree to consistently practice contraception if sexually active at least 7 days prior to enrollment and throughout the duration of the study
• Able to access and use a smartphone, tablet, computer, or other device connected to Wi-Fi or cellular network for completion of an eDiary

Exclusion Criteria:

• History of any clinically important cardiac, rheumatologic, endocrinologic, hematologic, hepatic, immunologic, metabolic, urologic, pulmonary, neurologic, dermatologic, psychiatric, renal, or other disease as determined by the Investigator. This includes a history of polyarthritis, nephropathy, pericarditis, myocarditis, or hypertension requiring current pharmacologic treatment.
• History of invasive GAS infection (such as toxic shock syndrome, necrotizing fasciitis, bloodstream infection, pleural empyema, meningitis) or poststreptococcal immune mediated disease (such as RHD, ARF, or APSGN)
• Known or suspected autoimmune disease, collagen vascular disease, or impairment/alteration of immune function (e.g., congenital or acquired immunodeficiency)
• Previous or existing diagnosis of human immunodeficiency virus, Hepatitis B virus, or Hepatitis C virus, or a positive serologic test at Screening
• History of malignancy or neoplasm, except for adequately treated basal cell or squamous cell skin cancer or in situ cervical cancer
• Bleeding disorder diagnosed by a physician (e.g., factor deficiency, coagulopathy, or platelet disorder requiring special precautions) resulting in clinically significant bruising or bleeding difficulties with IM injections or blood draws
• History of severe allergic reaction with generalized urticaria, angioedema, or anaphylaxis to any previous vaccination
• Oral temperature >38.0°C (>100.4°F) or acute illness within 3 days prior to study vaccination (subject may be rescreened)
• Confirmed elevated BP at Screening, defined as systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg measured seated after ≥5 minutes rest and confirmed by repeat measurement
• Physical examination indicating any clinically significant medical condition or inadequate venous access
• Any Grade ≥2 abnormal safety laboratory test at Screening
• Abnormal ESR, or CRP or C3 levels at Screening
• Confirmed microscopic hematuria (>10 RBC/mm³) on UA at Screening. If a potential confounder is present, a repeat UA may be performed during the Screening window; exclusion applies to confirmed microscopic hematuria on an evaluable specimen.
• Evidence of antecedent/recent GAS infection based on anti-DNase B titer ≥ the laboratory reported upper limit of normal (ULN) for the assay used at Screening. Participants with anti-DNase B titer ≥0.8×ULN and <ULN at the initial Screening visit are temporarily ineligible and may be re-screened with repeat anti-DNase B testing 7-21 days after the initial sample; participants will be excluded if the repeat anti-DNase B titer is ≥ULN or demonstrates a clinically meaningful increase of ≥20% relative to the initial screening value, in the absence of an alternative explanation.
• Positive GAS rapid NAAT at Screening or Day 1
• Any finding based on comprehensive TTE at Screening indicative of possible cardiac pathology, including valvular abnormalities defined as mild stenosis or regurgitation.
• Any finding on ECG that is indicative of possible cardiac pathology, including a prolonged PR interval or conduction abnormality
• Receipt of any investigational product within 30 days prior to enrollment into the study, currently participating in another study that includes receipt of an investigational product or procedure, or having plans to receive another investigational product(s) while on study
• Planned or actual administration of any licensed vaccine within 30 days before or after receipt of study vaccine, or within 14 days before or after receipt of study vaccine in the case of influenza and COVID-19 vaccines. Vaccines that are required emergently (e.g., tetanus vaccination in a participant with a contaminated wound) may be given at any time during the study.
• Received blood or blood product (including intravenous immunoglobulin) within 6 months of enrollment into the study
• Receipt of any immunosuppressive therapy, including systemic steroids at a dosage equivalent to ≥0.5 mg/kg/day of prednisone, chronic use of inhaled or nebulized high potency corticosteroids, or use of intra-articular or intrabursal corticosteroids within 1 year of the first study vaccination
• Body mass index (BMI) ≥32 kg/m2 or ≤18 kg/m2
• History of alcohol or drug abuse in the 5 years prior to enrollment, or any history of intravenous drug abuse
• Any medical, psychiatric, or social condition that in the judgment of the Investigator may interfere with the study objectives, impair a participant's ability to give informed consent, pose a risk to the participant, or prevent the participant from completing the study
• Employee of, or first degree relative of any person employed by the Sponsor, the contract research organization (CRO), the Investigator, study site personnel, or site