On Dec. 30, 2020, the NIH announced that the investigational vaccine known as mRNA-1273 was 94.1% efficacious in preventing symptomatic coronavirus disease 2019 (COVID-19), according to preliminary results from a Phase 3 clinical trial reported in the New England Journal of Medicine.

The vaccine also demonstrated efficacy in preventing severe COVID-19. Investigators identified no safety concerns and no evidence of vaccine-associated enhanced respiratory disease.