THEMBA II T-Cell Vaccine: Vaccination With saRNA COVID-19 Vaccines

Inclusion Criteria: 1. Healthy adults ≥ 18 years of age at time of enrollment. 2. Vaccinated with an EUA or approved vaccine against COVID-19 ≥ 3 months prior to enrollment on study or infection with COVID-19 ≥ 3 months prior to enrollment on study. 3. Able to understand and provide a signed informed consent that fulfills the relevant Institutional Review Board (IRB) or Independent Ethics Committee (IEC) guidelines. 4. Agrees to the collection of biospecimens (eg, nasopharyngeal \[NP\] swabs) and venous blood per protocol. 5. Ability to attend required study visits and return for adequate follow-up, as required by this protocol. 6. Temperature \< 38°C. 7. Agreement to practice effective contraception for female participants of childbearing potential and non-sterile males. Female participants of childbearing potential must agree to use effective contraception while on study until at least 1 month after the last dose of vaccine. Non-sterile male participants must agree to use a condom while on study until at least 1 month after the last dose of vaccine. Effective contraception includes surgical sterilization (eg, vasectomy, tubal ligation), two forms of barrier methods (eg, condom, diaphragm), intrauterine devices (IUDs), oral contraceptives, injectable contraceptives, patches, implants and abstinence. 8. HIV-positive participants must have been on anti-retroviral therapy for ≥ 4 weeks and have HIV-1 viral load \< 1,000 copies/mL at the time of enrollment. Exclusion Criteria: 1. Serious adverse reaction to any vaccine, any unrelated medication or any component of the investigational vaccine, including a history of anaphylaxis and symptoms of a severe allergic reaction and history of allergies in the past. 2. Confirmed current COVID-19, previous SARS-CoV-2 infection in the last \< 3 months, or PCR positive for SARS-CoV-2 at screening. 3. Vaccinated with an EAU-approved vaccine against COVID-19 in the last \< 3 months. 4. Pregnant or breastfeeding women. 5. Chronic lung disease (included COPD) as evidenced by one or more exacerbations requiring a course of steroids in the last year, or the requiring chronic low dose oral steroids to prevent exacerbations. Uncontrolled asthma, defined as requiring reliever inhaler (short-acting beta agonist or ipratromium bromide) more than twice a week is also excluded. 6. Bone marrow or organ transplant recipient 7. Extreme obesity (defined as BMI of 40 kg/m2 or higher). 8. Chronic kidney disease requiring dialysis. 9. History of liver disease. 10. Any disease associated with acute fever, or any infection. 11. Participants with acquired or hereditary immunodeficiencies other than well-controlled HIV are excluded from enrollment. 12. Current diagnosis of active tuberculosis. 13. History of hereditary, idiopathic or acquired angioedema. 14. No spleen or functional asplenia. 15. Chronic use (more than 14 continuous days) of any medications that may be associated with impaired immune responsiveness including, but not limited to, systemic corticosteroids exceeding 10 mg/day of prednisone equivalent, allergy injections, immunoglobulin, interferon, or immunomodulators. The use of low dose topical, ophthalmic, inhaled and intranasal steroid preparations will be permitted. 16. According to the judgement of the investigator any medical, psychiatric, psychological, social, occupational or other conditions that could affect the participants ability to sign informed consent, provide safety assessment data or comply with the requirements of the study protocol. 17. Assessed by the Investigator to be unable or unwilling to comply with the requirements of the protocol.