A Phase 3b/4, Open-label Study to Assess the Immunogenicity and Safety of mRNA COVID-19 Variant-containing Vaccine Formulations

Inclusion Criteria: * ≥65 years of age at the time of signing the informed consent OR ≥12 to \<65 years of age at the time of signing the informed consent with at least 1 risk factor for severe outcomes from COVID-19. * Female participants of childbearing potential may be enrolled in the study if not pregnant or breastfeeding, subject to other criteria specified in the study protocol. Exclusion Criteria: * History of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection within 6 months prior to enrollment. * Acutely ill or febrile within 72 hours prior to or at Day 1. * His…