Safety and Immunogenicity of COVI-VAC as a Booster Dose in Adults Previously Vaccinated Against COVID-19

Inclusion Criteria: 1. Men and women aged 18 to 65 years of age, inclusive, on the day of signing the ICF 2. Body mass index (BMI) ≤ 35 kg/m2 3. In good health with no history, or current evidence, of clinically significant medical conditions with particular reference to, but not restricted to, thromboembolic disorders, coronary heart disease, chronic obstructive lung disease, and no clinically significant test abnormalities that will interfere with participant safety, as defined by medical history, physical examination, vital signs (including oxygen saturation), and safety laboratory tests as determined by the Investigator 4. Previous receipt of an authorised mRNA or adenovirus-vectored COVID-19 vaccine with completion of vaccine regimen ≥ 3 months before Day 1 Exclusion Criteria: 1. Residents of residential care facilities 2. Pregnant or lactating women 3. Inadequate venous access for repeated phlebotomy 4. History of confirmed or suspected SARS-CoV-2 infection