By, the end of this week, both the Moderna and Pfizer-BioNTech coronavirus vaccines will have been authorized and starting to be shipped out.

What’s the difference between the two vaccines?

However, there are a few differences between the two drugs, an important one being the required storing temperatures. Moderna’s vaccine can be stored in normal freezers and does not require a super-cold transportation network, making it accessible for smaller facilities and local communities.

The U.S. Food and Drug Administration allowed clinical trials of Moderna’s vaccine to start on March 3 with its advanced stage clinical trial started on July 27, making it the first government-funded Phase 3 clinical trial for a COVID-19 vaccine in the U.S. Moderna then applied for emergency use authorization of the vaccine on November 30.


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Moderna’s vaccine against COVID-19 was 94.1% effective, occurring at least 14 days after the second dose, according to a briefing document released by an advisory committee to the FDA. During the trial, Moderna gave 15,000 participants the vaccine and another 15,000 the placebo. Over several months, 185 of the placebo participants developed COVID-19 with 30 severe cases and one death. Only 11 of the vaccinated participants developed the virus, none of them catching severe cases.

So what exactly differs between the Moderna and Pfizer-BioNTech vaccines?

Efficacy and Structure

Dr. Paul Offit, a member of the FDA’s vaccine advisory committee, claims both vaccines appear to be “roughly equivalent,” having similar efficacy levels of near 95%.

“Even though they’re both messenger RNA vaccines, they’re really different messenger RNA molecules, they have different so-called lipid delivery systems, meaning the sort of fatty droplet in which the messenger RNA is located,” Offit said on Monday. “That’s why they have different storage and handling characteristics.”


Unlike Pfizer’s vaccine that needs to be stored at about minus-75 degrees Celsius, Moderna’s vaccine can be kept at about minus-20 degrees Celsius, or about the temperature of an average home freezer. It can also be kept in a refrigerator for 30 days before it expires.

These differences in storage temperature suggest that Pfizer’s vaccine may be used more for major institutions with the resources to store like hospitals, while Moderna’s may be more useful to smaller facilities like a local chain or pharmacist.

Dosage, Timing and Safety

Moderna’s vaccine is administered as two 100-microgram doses given 28 days apart while Pfizer’s Is administered as two 30-microgram doses given 21 days apart.

According to the briefing document to the FDA, the vaccine has a “favorable” safety profile with “no specific safety concerns identified.” The most common reactions from the vaccine include injection site pain, fatigue, headache, muscle pain, joint pain and chills.

The vaccine advisory committee from the FDA is meeting Thursday to review whether to recommend Moderna’s vaccine be used for emergencies. The decision is expected by Friday.

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