MONDAY, Jan. 4, 2021 (HealthDay News) -- The mRNA-1273 vaccine has 94.1 percent efficacy for preventing COVID-19 illness, according to a study published online Dec. 30 in the New England Journal of Medicine.
Lindsey R. Baden, M.D., from Brigham and Women's Hospital in Boston, and colleagues conducted a phase 3 randomized trial at 99 centers across the United States. A total of 30,420 individuals at high risk for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or its complications were randomly assigned to receive either two intramuscular injections of mRNA-1273 or placebo 28 days apart (15,210 in each group). The primary end point was prevention of COVID-19 illness 14 days after the second injection.
The researchers found that symptomatic COVID-19 illness was confirmed in 185 and 11 participants in the placebo and mRNA-1273 groups, respectively (56.5 versus 3.3 per 1,000 person-years), resulting in vaccine efficacy of 94.1 percent. Similar efficacy was observed in key secondary analyses, including assessment 14 days after the first dose, analyses that included individuals with evidence of SARS-CoV-2 infection at baseline, and analyses in those aged 65 years or older. Severe COVID-19 occurred in 30 individuals, with one death; all were in the placebo group. After vaccination, moderate, transient reactogenicity occurred more often in the mRNA-1273 group; severe adverse events were rare, with similar incidence between the two groups.
"The finding of fewer occurrences of symptomatic SARS-CoV-2 infection after a single dose of mRNA-1273 is encouraging; however, the trial was not designed to evaluate the efficacy of a single dose, and additional evaluation is warranted," the authors write.
Several authors disclosed financial ties to pharmaceutical companies, including Moderna, the manufacturer of the mRNA-1273 vaccine.