Phase 2b Booster Vaccination (TURKOVAC) Against COVID-19

This phase 2b study aims to determine the efficacy, safety, and immunogenicity of a booster dose of TURKOVAC vaccine administered to subjects who have passed at least 90 days and at most 240 days after the second dose of the first course of Comirnaty (Code name: BNT162b2) vaccine. Efficacy will be evaluated by spike-specific antibody response and neutralizing antibody levels on days 0, 28 (all subjects), 48, 84 and 168 days (50% of subjects). For the booster dose, subjects will be assigned open-label according to randomization (1:1) for 2 different arms. Comparing the efficacy, safety, and immunogenicity results of different series of TURKOVAC vaccines (TURKOVAC-Koçak and TURKOVAC-Dollvet) produced in different production facilities are the secondary objectives of the study. The booster dose vaccine arms are as follows: * TURKOVAC-Koçak * TURKOVAC-Dollvet