HealthDay News – The mRNA-1273 vaccine has 94.1% efficacy for preventing COVID-19 illness, according to a study published online December 30 in the New England Journal of Medicine.

Lindsey R. Baden, MD, 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 2 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 vs 3.3 per 1000 person-years), resulting in vaccine efficacy of 94.1%. 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 1 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 2 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.


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Several authors disclosed financial ties to pharmaceutical companies, including Moderna, the manufacturer of the mRNA-1273 vaccine.

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