A Safety and Immunogenicity Trial of OCU500, ChAd36 Vector Encoding SARS-CoV-2 Spike Vaccine Via Intranasal and Inhalational Routes in Previously Vaccinated Adults

Inclusion Criteria: 1. Provides written informed consent before initiation of any study procedures. 2. Able to understand and agree to comply with planned study procedures and be available for all study visits. 3. Non-pregnant adults, 18 through 64 years of age at the time of study product administration. 4. Participants of childbearing potential\* must agree to use or have practiced true abstinence\*\* or use at least one acceptable primary form of contraception.\*\*\* \*These criteria apply to females who are in a heterosexual relationship and are of childbearing potential. Not of childbearing potential include post-menopausal females (defined as having a history of amenorrhea for at least one year) or a documented status as being surgically sterile (hysterectomy, bilateral oophorectomy, or tubal ligation/salpingectomy). \*\*True abstinence is 100 percent of the time, no sexual intercourse (penis enters the vagina). Periodic abstinence \[e.g., calendar, ovulation, symptothermal, post-ovulation methods\] and withdrawal are not acceptable methods. \*\*\*Acceptable forms of primary contraception include a monogamous relationship with a vasectomized partner who has been vasectomized for 180 days or more before the participant's study product administration, a copper intrauterine device, a levonorgestrel-releasing intrauterine device, a progestin-only oral contraceptive pill, a depot medroxyprogesterone injection, or a progestin implant. Combined hormonal contraceptives containing estrogen, including combined oral contraceptive pills, transdermal patches, and vaginal rings, are not acceptable for this trial. Must have used at least one acceptable primary form of contraception for at least 30 days before study product administration and agree to continue at least one acceptable primary form of contraception through 60 days after study product administration. 5. Participants of childbearing potential must have a negative urine pregnancy test at screening and within 24 hours before study product administration. 6. In general, good health.\* \*As determined by medical history and physical examination, including vital signs, to evaluate acute or ongoing chronic medical diagnoses/conditions that have been present for at least 90 days, which would affect the assessment of participant safety. Chronic medical diagnoses/ conditions should be stable for the last 30 days (i.e., no hospitalization, ER, or urgent care for the condition). This includes no change in chronic prescription medication, dose, or frequency due to deterioration of the chronic medical diagnosis or condition within the 30 days preceding the study product administration. Any prescription change that is due to a change of health care provider, insurance company, etc., or done for financial reasons, and in the same class of medication, will not be considered a deviation of this inclusion criterion. Participants may be on chronic or as-needed (prn) medications if, in the opinion of the participating site PI or appropriate sub-investigator, they pose no additional risk to participant safety or assessment of reactogenicity and immunogenicity. 7. Receipt of a complete primary COVID-19 vaccine series and at least one booster\* with last vaccination at least 16 weeks before study product administration. \*Booster may be either homologous or heterologous to the primary vaccine series. It must be an FDA-authorized/licensed vaccine, though doses may have been received as part of a clinical trial. 8. Clinical screening laboratory evaluations are within normal reference ranges or grade 1 with no clinical significance (NCS) per investigator discretion.\* \*(White Blood Cells \[WBCs\] with differential \[diff\], hemoglobin \[Hgb\], platelets \[PLTs\], PTT, PT, Alanine Transaminase \[ALT\], Aspartate Transaminase \[AST\], Creatinine \[Cr\], Alkaline Phosphatase \[ALP\], Total Bilirubin \[T. Bili\]). ALT, AST, ALP, T. Bili, and creatinine values that are below the reference range will not be exclusionary, as these values below the reference range are clinically insignificant. 9. Must agree to have samples stored for secondary research. 10. Must complete a Test of Understanding (ToU) before enrollment by answering 90 percent of questions correctly at least once in 3 attempts. Exclusion Criteria: 1. Positive SARS-CoV-2 PCR at screening. 2. Abnormal vital signs (Grade 1 or higher).\* \*Grade 1 or higher is equivalent to: Systolic blood pressure (SBP) = 141 mmHg or = 89 mmHg Diastolic blood pressure (DBP) = 91 mmHg Heart rate (HR) is = 101 beats per minute or = 54 beats per minute Oral temperature = 38.0 degrees Celsius (100.4 degrees Fahrenheit) 3. History of SARS-CoV-2 infection within the prior 16 weeks OR receipt of any COVID-19 vaccine within the prior 16 weeks before study product administration. 4. Participant who is pregnant or breastfeeding or less than 12 weeks post partum at the time of study product administration. 5. Participant has donated blood or plasma within 4 weeks prior to study product administration, or does not agree to refrain from blood or plasma donation until Day 181. 6. Receipt of antibody or blood-derived products within 90 days before study product administration. 7. Any significant medical or psychiatric diseases or any other condition that, in the opinion of the site PI or appropriate sub-investigator, precludes study participation.\* \*Significant self-reported or medically reported medical or psychiatric conditions include, but are not limited to drug or alcohol abuse within 6 months of enrollment, significant kidney disease, liver disease, history of hematologic malignancies, ongoing malignancy or recent diagnosis of malignancy in the last five years, excluding treated basal cell and squamous cell carcinoma of the skin, and cervical carcinoma in situ, which are allowed. 8. Any respiratory disease, including but not limited to chronic obstructive pulmonary disease (COPD), asthma, inter