Moderna Says Its COVID-19 Vaccine is 94.1 Percent Effective

There are now two coronavirus vaccines available in the United States. Find out what happens next.

doctor giving vaccine to woman

Medically reviewed in December 2020

Updated on November 16, 2020

Moderna reveals its coronavirus vaccine, known as mRNA-1273, is 94.1 percent effective against COVID-19. There are now two vaccines available in the United States shown in trials to be safe and highly effective against the disease.

For Moderna's Phase 3 trial, 15,000 volunteers were given a placebo, or a shot of saline. Another 15,000 volunteers received the experimental vaccine. Of these people, 37 percent were from racial and ethnic minority groups, which is similar to the diversity of the overall U.S. population.

High-risk groups also account for 42 percent of the participants, including more than 7,000 people older than 65, more than 5,000 people who are younger than 65 but have chronic diseases that put them at higher risk of severe COVID-19, such as diabetes, severe obesity and heart disease.

An FDA data review released on December 16 confirmed that the vaccine is highly successful with an efficacy rate of 94.1 percent. The review also concluded that the vaccine was safe and well-tolerated among the participants.

How Moderna’s vaccine works
The vaccine candidate, mRNA-1273, is an mRNA vaccine.

Traditional vaccines for viruses are made from a weakened or inactive virus, but Moderna’s vaccine is not made from SARS-CoV-2, the coronavirus that causes COVID-19.

Instead, it works by delivering pieces of genetic material that carry instructions for making the COVID-19 spike protein, which is the protein that SARS-CoV-2 uses to infect cells.

The genetic code, or mRNA, is packaged inside a slippery coating that allows it to slide into cells and tell them to make the spike protein. This prompts an immune response to protect you from catching COVID-19.

Moderna’s vaccine is one of two mRNA COVID-19 vaccines that have been granted Emergency Use Authorization (EUA) by the U.S. Food and Drug Administration (FDA) and approved by the U.S. Centers for Disease Control and Prevention (CDC) for use in the United States. The other was developed by Pfizer in partnership with Germany’s BioNTech.

On November 18, Pfizer and the German drugmaker, BioNTech, announced the first set of complete results from their ongoing coronavirus vaccine trial. The results suggests it’s 95 percent effective against COVID-19, starting 28 days after the first dose.

The effectiveness of the vaccine was similar for both men and women and people of different races and ethnicities. For adults older than 65, the vaccine was shown to be 94 percent effective. No serious safety concerns have been reported.

One key difference between Pfizer and Moderna
Moderna’s vaccine remains stable for 30 days at 36° to 46°F—the temperature of a standard home or medical refrigerator.

At a colder temperature of -4°F, it could remain stable for up to six months, while it may last for 12 hours at room temperature.

Moderna points out that most pharmaceutical distribution companies have the ability to store and ship products globally at -4°F.  

“We believe that our investments in mRNA delivery technology and manufacturing process development will allow us to store and ship our COVID-19 vaccine candidate at temperatures commonly found in readily available pharmaceutical freezers and refrigerators,” said Juan Andres, Chief Technical Operations and Quality Officer at Moderna in a November 16 news release.

Pfizer’s vaccine, on the other hand, must be stored in an ultra or deep freezer at about -94° F in order to remain effective. The company noted that this is a potential barrier to its widespread distribution.

“Risks and uncertainties include, among other things…challenges related to our vaccine candidate’s ultra-low temperature formulation and attendant storage, distribution and administration requirements, including risks related to handling after delivery by Pfizer,” the company stated in a November 9 news release. Pfizer added there is a possible risk that the company might not be able to successfully develop non-frozen formulations of its COVID-19 vaccine. The company reports, however, that it has developed specially designed, temperature-controlled thermal shippers that use dry ice to maintain the necessary ultra-low temperatures. These shipping units can be used as temporary storage of the vaccine for up to 15 days if they are refilled with dry ice. Each unit is equipped with a heat senor to track its location and temperature during shipment.

What happens next
Moderna is working with the U.S. Centers for Disease Control and Prevention (CDC), Operation Warp Speed and vaccine distributor, McKesson, to prepare to distribute its vaccine around the world.  

By the end of 2020, the company expects to have approximately 20 million doses of mRNA-1273 ready to ship in the United States. Moderna also plans to make up to one billion doses globally in 2021.

Article sources open article sources

Moderna. “Moderna’s COVID-19 Vaccine Candidate Meets its Primary Efficacy Endpoint in the First Interim Analysis of the Phase 3 COVE Study.” Nov 16, 2020.
Moderna. “Moderna’s Fully Enrolled Phase 3 COVE Study of mRNA-1273.” Oct 22, 2020.
National Institute of Allergy and Infectious Diseases. “Promising Interim Results from Clinical Trial of NIH-Moderna COVID-19 Vaccine.” Nov 16, 2020.
Pfizer. Pfizer and BionTech Announce Vaccine Candidate Against COVID-19 Achieved Success in First Interim Analysis From Phase 3 Study. Nov 9, 2020.
Moderna. “Moderna Announces Longer Shelf Life for its COVID-19 Vaccine Candidate at Refrigerated Temperatures.” Nov 16, 2020.

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