The duration of participation in the initial, double-blind, primary series design of the study will be approximately 365 days post-last injection (ie, approximately 386 days total) for each participant.~Based on decisions of the Study OG, Stage 1 and Stage 2 participants will be invited to participate in an unblinded Crossover / Booster study design with duration as follows:~For participants who initially received vaccine: 12 months post-booster (ie, approximately 18 to 24 months)~For participants who initially received placebo: ≥ 4 months post-last dose of the primary series + 12 months post-booster (ie, approximately 28 to 34 months)~For participants who do not consent to continue in the unblinded Crossover / Booster part of the study, all study procedures will be stopped and participants will be discontinued from the study.
The purpose of this Phase III study is to assess the efficacy, safety, and immunogenicity of two CoV2 preS dTM-AS03 vaccines (monovalent and bivalent) as part of primary series vaccinations in a multi-stage approach, as well as a booster injection of a CoV2 preS dTM-AS03 vaccine, in adults 18 years of age and older.~A total of approximately 21 046 participants are planned to be enrolled (5080 per study intervention group in Stage 1 and 5443 per study intervention group in Stage 2).~Initial, double-blind, primary series study design is planned for 365 days post-last Initial injection (ie, approximately 386 days total) for each participant.~Based on decisions of the Study Oversight Group, Stage 1 and Stage 2 participants will be invited to participate in an unblinded Crossover / Booster study design with duration as follows:~For participants who initially received vaccine: 12 months post-booster (ie, approximately 18 to 24 months)~For participants who initially received placebo: ≥ 4 months post-last dose of the primary series + 12 months post-booster (ie, approximately 28 to 34 months)~For participants who do not consent to continue in the unblinded Crossover / Booster part of the study, all study procedures will be stopped and participants will be discontinued from the study.