Here we show that mRNA-1273 induces both potent neutralizing antibody responses to wild-type (D614) and D614G mutant2 SARS-CoV-2 and CD8 T cell responses, and protects against SARS-CoV-2 infection in the lungs and noses of mice without evidence of immunopathology. mRNA-1273 is currently in Phase 3 efficacy evaluation.