What is the Moderna (mRNA-1273) COVID-19 vaccine?

Updated: Jan 12, 2021
  • Author: Setu K Patolia, MD, MPH; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Analogous to the BNT162b2 vaccine, the mRNA-1273 encodes the SARS-CoV-2 spike protein. After being tested on mice and rhesus macaques, the phase 1 trial of this vaccine was reported on two doses of the vaccine given 28 days apart. This report, published on November 12, 2020,  was an open-label trial with 45 patients comparing the 25-μg and the 100-μg dose. In this phase 1 clinical trial, the major adverse effects included fatigue, chills, headache, myalgia, and injection site pain. No major adverse events were noticed. More recently, on December 17, 2020, the original trial was expanded to include an additional 40 patients who were aged 56-70 years or older than 71 years. Again, no severe adverse events were noted and it seemed that more moderate systemic adverse events were associated with the 100-μg dose. [64]

Although the results of the phase 3 trial are pending publication in a peer-reviewed journal, the preliminary release shows the Moderna vaccine is 94.1% effective against SARS CoV-2 infection and 100% effective in preventing severe COVID-19.

The FDA issued an Emergency Use Authorization for the vaccine on December 18, 2020.

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