Study of Recombinant Protein Vaccines With Adjuvant as a Primary Series and as a Booster Dose Against COVID-19 in Adults 18 Years of Age and Older

The primary objectives of the study are: To assess the safety profile of the study vaccines in each study intervention group. To assess the neutralizing antibody profile after primary series vaccination in SARS-CoV-2-naïve adults. To demonstrate that a booster dose of monovalent or bivalent SARS-CoV-2 vaccine given to adults previously vaccinated with an authorized/approved COVID-19 vaccine induces an immune response that is non-inferior to the response induced by a twodose priming series with the monovalent vaccine, and superior to that observed immediately before booster. The secondary objectives of the study are: To assess the neutralizing and binding antibody profiles after primary series vaccination at pre-defined time points during the study. To assess the neutralizing and binding antibody responses of booster vaccination. To describe the occurrences of laboratory-confirmed symptomatic COVID19 after primary series and booster vaccination. To describe the occurrences of serologically-confirmed SARS-CoV-2 infection after primary series vaccination.