The study will evaluate the safety, tolerability, and immunogenicity of 3 different SARS-CoV-2 RNA vaccine candidates against COVID-19 and the efficacy of 1 candidate: The study consists of 2 parts: Phase 1: to identify preferred vaccine candidate(s) and dose level(s) Phase 2/3: an expanded cohort and efficacy part. This is a Phase 1/2/3, randomized, placebo-controlled, observer-blind, dose-finding, vaccine candidate-selection, and efficacy study in healthy individuals. Why Should I Register and Submit Results?.