Phase 2/3 Heterologous Boosting Study With Different Dose Levels of Monovalent SARS-CoV-2 rS Vaccines

The ongoing COVID-19 pandemic has reached a stage where it is necessary to stablish the framework for periodic national vaccination campaigns.The present study aims to investigate the safety and immunogenicity of different booster dose levels of monovalent and bivalent vaccines in adults ≥ 50 years of age who have already been immunized with ≥ 3 doses of a COVID-19 prototype or bivalent licensed mRNA vaccine. The Boosters of investigational products will be administered ≥ 90 days after the participants received their third dose of a COVID-19 prototype or bivalent licensed mRNA vaccine. Approximately 1,980 participants ≥ 50 years of age who have received a regimen of ≥ 3 doses of a coronavirus disease 2019(COVID-19) vaccine (the last vaccine could have been a bivalent licensed mRNA vaccine) will be included in this study. The last COVID-19 vaccine dose should have been administered ≥ 90 days prior to Day 0. Approximately 1,800 participants will be randomly assigned in a 1:2:2:2:2:1 ratio to receive NVX-CoV2373 or NVC-CoV2601 in a double-blinded fashion into 1 of 6 monovalent vaccine groups (vaccine groups A to G). Following completion of enrollment into the 6 monovalent vaccine groups, 180 participants will be enrolled in vaccine group G to receive a bivalent licensed mRNA vaccine in an open-label fashion.