Efficacy and Safety of the mRNA-1273 SARS-CoV-2 Vaccine.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 33378609 · doi:10.1056/NEJMoa2035389
What was done
In a phase 3, observer-blinded, placebo-controlled trial across 99 centers in the United States, 30,420 volunteers at high risk for SARS-CoV-2 infection or its complications were randomly assigned 1:1 to receive two intramuscular injections of mRNA-1273 (100 μg) or placebo 28 days apart. The primary end point was the prevention of symptomatic Covid-19 illness starting at least 14 days after the second injection in participants without prior infection.
What was found
Among 30,420 participants (15,210 per group), symptomatic Covid-19 occurred in 185 participants in the placebo group (56.5 per 1000 person-years; 95% CI, 48.7 to 65.3) and in 11 participants in the mRNA-1273 group (3.3 per 1000 person-years; 95% CI, 1.7 to 6.0), demonstrating a vaccine efficacy of 94.1% (95% CI, 89.3 to 96.8%; P<0.001). Severe Covid-19 occurred in 30 participants (one fatal), all in the placebo group. Moderate, transient reactogenicity was more frequent in the vaccine group, but serious adverse events were rare and similar between groups.
Why it matters
This trial established the high efficacy and short-term safety of the mRNA-1273 vaccine in preventing symptomatic and severe SARS-CoV-2 infection in adults.
Limits
The trial took place only in the United States and short-term follow-up was reported. The abstract does not evaluate long-term durability of protection, asymptomatic infection, or efficacy against emerging SARS-CoV-2 variants.
Cited by
- supports The original randomized controlled trials for the mRNA COVID-19 vaccines enrolled a total of 75,000 participants.