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Moderna COVID-19 vaccine trial results

A new report presents the latest clinical data on the efficacy of the mRNA COVID-19 vaccine developed by Moderna.

Over the past few months, the development and testing of vaccines to help reduce transmission of the SARS-CoV-2 virus has been a priority. One of these vaccines is mRNA-1273, which is a COVID-19 vaccine developed by a collaboration of two companies, Moderna and the National Institute of Allergy and Infectious Diseases (NIAID).  Moderna is a biotechnology company originally from Cambridge, Massachussets, and the NIAID is a branch of the United States’ National Institutes of Health (NIH).

This vaccine contains an encapsulated messenger ribonucleic acid (mRNA) that encodes for the spike protein that is present on the surface of the SARS-CoV-2 virus.  Although SARS-CoV-2 is the virus that causes COVID-19, this vaccine cannot give someone COVID-19 because it does not contain the virus itself.  Instead, this spike protein mRNA teaches the body to recognize the SARS-CoV-2 virus and develop an immune response against it so the body can fight off the virus more efficiently if it’s exposed to it.

The idea for making the vaccine based on the SARS-CoV-2 spike protein was based on the vaccine for the structurally similar coronavirus that caused the SARS outbreak in the early 2000s. Due to the severity of the COVID-19 pandemic, vaccine development was heavily prioritized in scientific research, helping to speed up development. 

To examine the safety and efficacy of this Moderna COVID-19 vaccine, a phase 3 clinical trial was conducted at nearly 100 centers in the United States.  The findings of this study were collected and a reported in the New England Journal of Medicine.

The study included 30,420 volunteers; 50% of the participants received the Moderna COVID-19 vaccine and the other 50% received a placebo.  The study group consisted of approximately equal proportions of males and females, and the average age of the volunteers was 51. The trial ran from July 27, 2020, to November 25, 2020.  The participants were all monitored for 28 days for potential adverse reactions, and they were monitored after to see whether they developed COVID-19.

The study found that the Moderna COVID-19 vaccine was 94.1% effective in preventing symptomatic COVID-19 in this clinical trial.  Furthermore, there were no significant safety concerns, although approximately half of the participants in the vaccine group experienced side effects including fatigue, muscle aches, and headache in the two days following vaccination.

It is important to note that this trial only determined the vaccine’s efficacy in preventing symptomatic COVID-19; it did not determine whether or not this was necessarily effective in preventing asymptomatic COVID-19 development or COVID-19 transmission.  More research is needed to determine whether or not the vaccine is effective against asymptomatic COVID-19 development and transmission.


Baden, L.R., El Sahly, H.M., Essink, B., Kotloff, K., et al (2020). Efficacy and Safety of the mRNA-1273 SARS-CoV-2 Vaccine. The New England Journal of Medicine. Doi: 10.1056/NEJMoa2035389.

Centers for Disease Control and Prevention. (2020 December 18). U.S. Department of Health & Human Services. Retrieved 2021 January 9, from https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/mrna.html

EurekAlert! (2020 December 30). American Association for the Advancement of Science. Retrieved 2021 January 9, from https://www.eurekalert.org/pub_releases/2020-12/nioa-pro123020.php

Image by cromaconceptovisual from Pixabay 


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