Dec 31, 2020
The investigational vaccine known as mRNA-1273 was 94.1 percent 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 (VAERD).
The vaccine was co-developed by Moderna, Inc., a biotechnology company based in Cambridge, Massachusetts, and the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. Moderna and NIAID previously shared initial results from the COVE trial. On December 18, 2020, the FDA issued an Emergency Use Authorization allowing Moderna to make the vaccine available for the prevention of COVID-19 in adults in the United States.
The trial was led by principal investigators Lindsey R. Baden, MD, of Brigham and Women's Hospital in Boston, Hana M. El-Sahly, MD, of Baylor College of Medicine in Houston, and Brandon Essink, MD, of Meridian Clinical Research. The trial was implemented under the U.S. government's Operation Warp Speed program and supported by NIAID and the Biomedical Advanced Research and Development Authority (BARDA) of the U.S. Department of Health and Human Services' Office of the Assistant Secretary for Preparedness and Response.
The trial began on July 27, 2020, and enrolled 30,420 adult volunteers at clinical research sites across the United States. Volunteers were randomly assigned 1:1 to receive either two 100 microgram (mcg) doses of the investigational vaccine or two shots of saline placebo 28 days apart. The average age of volunteers is 51 years. Approximately 47 percent are female, 25 percent are 65 years or older, and 17 percent are under the age of 65 with medical conditions placing them at higher risk for severe COVID-19. Approximately 79 percent of participants are white, 10 percent are Black or African American, 5 percent are Asian, 0.8 percent are American Indian or Alaska Native, 0.2 percent are Native Hawaiian or Other Pacific Islander, 2 percent are multiracial, and 21 percent (of any race) are Hispanic or Latino.
From the start of the trial through November 25, 2020, investigators recorded 196 cases of symptomatic COVID-19 occurring among participants at least 14 days after they received their second shot. Some 185 cases (30 of which were classified as severe COVID-19) occurred in the placebo group and 11 cases (zero of which were classified as severe COVID-19) occurred in the group receiving mRNA-1273. The incidence of symptomatic COVID-19 was 94.1 percent lower in those participants who received mRNA-1273 as compared to those receiving placebo.
Investigators observed 236 cases of symptomatic COVID-19 among participants at least 14 days after they received their first shot, with 225 cases in the placebo group and 11 cases in the group receiving mRNA-1273. The vaccine efficacy was 95.2 percent for this secondary analysis.
There were no concerning safety issues with vaccination, according to the authors. Local reactions to the vaccine were generally mild. About 50 percent of participants receiving mRNA-1273 experienced moderate-to-severe side effects—such as fatigue, muscle aches, joint pain and headache—after the second dose, which resolved in most volunteers within two days.
Investigators also observed no evidence of VAERD among those who received mRNA-1273. This rare complication was seen in individuals vaccinated with a whole-inactivated respiratory syncytial virus (RSV) vaccine in the 1960s, before there was a capacity to define protein structures and measure immune responses with precision. VAERD can occur when a vaccine induces an immune response that is not strong enough to protect against infection.
Although mRNA-1273 is highly efficacious in preventing symptomatic COVID-19, there is not yet enough available data to draw conclusions as to whether the vaccine can impact SARS-CoV-2 transmission. Preliminary trial data suggests there may be some degree of prevention of asymptomatic infection after a single dose. Additional analyses are underway of the incidence of asymptomatic infection and viral shedding post-infection to understand the vaccine's impact on infectiousness.
The authors concluded by discussing the unprecedented efficiency of the candidate vaccine's development, noting, "this process demonstrates what is possible in the context of motivated collaboration among key sectors of society including academia, government, industry, regulators, and the larger community."
- This press release was originally published on the National Institute of Allergy and Infectious Diseases website