The purpose of the study is to evaluate the safety and immunogenicity of a novel Venezuelan Equine Encephalitis virus (VEEV) vaccine (V4020) for the first time in humans compared to placebo when administered by subcutaneous or intramuscular injection.

The primary objective of the study will be to measure safety. The primary endpoint measures to assess this objective will include but not be limited to

• Frequency and nature of adverse events (AEs) reported or observed in participants;
• Relatedness between AEs and vaccine administration;
• Interventions or therapy required by participants experience vaccine related adverse events;
• Resolution or outcome of AEs. Secondary Objectives and Endpoints Two main immunogenicity objectives will be assessed to include the number considered adequately immunized, and the magnitude and durability of titer responses.

Inclusion Criteria:

• Participants must meet all the following criteria to be included in the study:

  1. 18-50 years old at time of consent.
  2. Have VEE virus PRNT80 < 1:10.
  3. If biologic female of childbearing potential, must agree to have a serum pregnancy test 3 days before vaccine administration. (Exceptions for those with documented hysterectomy or ≥ 3 years of menopause.) The results must be negative. Females of child-bearing potential must agree not to become pregnant for at least 3 months after receipt of vaccination. They must also agree to use an acceptable form of birth control with less than a 1% failure rate as determined by the US Centers for Disease Control (https://www.cdc.gov/reproductivehealth/ contraception/index.htm).
  4. Sign and date the approved informed consent document, a separate consent form for HIV testing, and HIPAA Authorization.
  5. Medical exam (including history, concomitant medications, physical examination, and laboratory tests) negative for acute morbidities within 60 days of planned first administration of vaccine.
  6. Be willing to return for all follow-up visits.
  7. Maintain a symptom diary and bring it to all follow-up appointments. Participants will be provided a template and instructed on how to record dates, times, and details of relevant symptoms (e.g. severity, concurrent activity).
  8. Agree to report any AEs that may or may not be associated with administration of the vaccine for at least 28 days after administration and agree to report all SAEs (for example, resulting in hospitalization) for the duration of participation in the study.
  9. Agree to take appropriate measures to avoid mosquito and other insect bites if experiencing vaccine-related symptoms following vaccination until those symptoms resolve, and/or tests for vaccine virus shedding become negative.
  10. Agree to defer blood, bone marrow and organ donation for 1 year after vaccine receipt.

Exclusion Criteria:

• Participants meeting any of the following criteria will be excluded from the study:

  1. Have received experimental VEE vaccine previously or had known VEE exposure.
  2. Have family history (first degree relative) of diabetes mellitus (any type), a personal or family history of gestational diabetes, a confirmed elevated fasting serum glucose test (> 125 mg/dL), or a hemoglobin A1c > 5.6%. (At the PI's discretion, a participant may enroll if the family history of diabetes is only of late onset in an elderly parent.)
  3. Acute or chronic, clinically significant hematologic, pulmonary, cardiovascular, or hepatic or renal functional abnormality as determined by the investigator based on medical history, physical examination, EKG, and/or laboratory screening test.
  4. Have a personal history of an immunodeficiency or received treatment with an immunosuppressive medication, such as systemically administered glucocorticoids (e.g., prednisone) within
  1. month before planned administration of the vaccine or with other immunosuppressive therapies within 6 months of planned administration of the vaccine. Other immunosuppressive therapies include all cancer chemotherapeutic agents, drugs to prevent transplant rejection, interferons, monoclonal antibodies, protein kinase inhibitors, methotrexate, TNF (tumor necrosis factor) inhibitors, and any other clinically significant immunosuppressive medication as determined by the PI. Current administration of topical, inhalational, or intranasal glucocorticoids is not excluded. 5. Breastfeeding female. 6. Have any known allergies to components of the vaccine. 7. Receipt or planned receipt of any experimental or licensed vaccine, except for a licensed seasonal influenza, coronavirus, or other required health maintenance vaccine, within the period 30 days prior to initial injection through 60 days after the Day 70 follow-up. (~ 6-month period in total) 8. A history of prior vaccination against or confirmed infection with eastern equine encephalitis (EEE) virus, western equine encephalitis (WEE) virus, chikungunya (CHIK) virus or Venezuelan equine encephalitis (VEE) Virus. Those found to have pre-existing protective antibody responses against VEEV at baseline will also be excluded. 9. Have any unresolved AE resulting from a previous immunization. 10.Any chronic or active neurologic disorder, including seizures and epilepsy, excluding a single febrile seizure as a child. 11. Syncopal episode within 12 months of screening. 12.Suspected or known current alcohol abuse as defined by the American Psychiatric Association in DSM V (Diagnostic and Statistical Manual of Mental Disorders-5th edition) 13.Chronic or active illicit and/or intravenous drug use by history. 14.Any other significant finding that, in the opinion of the investigator, would increase the risk of the individual having an adverse outcome from participating in this study. 15.Have an acute or chronic medical condition that, in the judgment of the PI, would impact participant safety. 16.Have been in contact with a suspected COVID-19, influenza and/or RSV patient within the past 14 days will need to wait an additional 14 days or have negative test laboratory test results before enrolling. 17.Participants who are likely to have direct contact with all equine species (e.g., equestrians, horse farmers) during the clinical trial period will be excluded.

During the randomized phase, Sponsor personnel and the site pharmacist will be unblinded while the investigator, clinical site, and participants participating in the study will remain blinded.

The study is designed to keep participants and investigators blinded until completion of the clinical phase of the trial and monitoring of the clinical data. During the study all efforts will be made to keep participants and investigators unaware of participant assignment.