Moderna COVID-19 Vaccine Candidate Achieves 94.5% Efficacy in Phase 3 Trial


Moderna announced safety and efficacy data from the phase 3 COVE trial that found mRNA-1273 94.5% effective in preventing infection with SARS-CoV-2.

Biopharmaceutical company Moderna today announced that the phase 3 trial of its vaccine candidate mRNA-1273 against COVID-19 had met prespecified efficacy criteria, with the vaccine achieving efficacy of 94.5%.

The announcement came after the company was notified by the independent NIH-appointed Data Safety Monitoring Board reviewing the trial.

The COVE study enrolled more than 30 000 participants in the US and is being conducted in collaboration with the National Institute of Allergy and Infectious Diseases (NIAID) and the Biomedical Advanced Research and Development Authority (BARDA).

The study’s primary endpoint is based on analysis of COVID-19 cases confirmed and adjudicated beginning 2 weeks following the second of 2 doses of the vaccine.

This is the first interim analysis and was based on 95 cases of COVID-19—90 observed in the placebo group and 5 in the group receiving mRNA-1273, resulting in the point estimate of vaccine efficacy of 94.5% (p <.0001).

Severe cases of COVID-19, as defined by the study protocol, were analyzed as a secondary endpoint in this analysis; 11 cases were observed, all in the placebo group and none in mRNA-1273-vaccinated group.


The Phase 3 COVE trial is a randomized, 1:1 placebo-controlled study testing mRNA-1273 at the 100 µg dose level in 30,000 participants in the US, ages 18 and older. The primary endpoint is the prevention of symptomatic COVID-19 disease. Key secondary endpoints include prevention of severe COVID-19 disease and prevention of infection by SARS-CoV-2. The trial will continue to accrue additional data relevant to safety and efficacy even after an EUA is submitted.

The 95 participants infected with
the SARS-CoV2 virus included
15 older adults (aged 65+)
and 20 participants identifying
as being from diverse communities
including 12 Hispanic or
LatinX, 4 Black or African
Americans, 3 Asian Americans
and 1 multiracial participant.

The DSMB found no significant safety concerns associated with mRNA1273; the vaccine was generally well tolerated with the majority of adverse events either mild or moderate. Severe events included injection site pain after the first dose and after the second dose, fatigue, myalgia/arthralgia, headache, pain and erythema at the injection site. All were generally short lived. These data are subject to change based on ongoing analysis of additional phase 3 COVE study data and final analysis.

“This positive interim analysis from our Phase 3 study has given us the first clinical validation that our vaccine can prevent COVID-19 disease, including severe disease,” said Stéphane Bancel, chief executive officer of Moderna, in the company press release. “This milestone is only possible because of the hard work and sacrifices of so many. I want to thank the thousands of participants in our Phase 1, Phase 2 and Phase 3 studies, and the staff at our clinical trial sites who have been on the front lines of the fight against the virus. They are an inspiration to us all.

"We look forward to the next milestones of submitting for an EUA in the U.S., and regulatory filings in countries around the world, while we continue to collect data on the safety and efficacy of the vaccine in the COVE study," added Bancel. We remain committed to and focused on doing our part to help end the COVID-19 pandemic.”

Submission for an Emergency Use Authorization (EUA) with the USFDA will be made in the next few weeks and will be based on the final safety and efficacy data (with a median duration of at least 2 months). 

The news comes 1 week after Pfizer/BioNTech announced more than 90% efficacy for their vaccine against SARS-CoV-2 infection in the first interim analysis of phase 3 study.

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