(CNN) Moderna's coronavirus vaccine candidate is similar to the Pfizer-BioNTech vaccine that was authorized and shipped out to the first Americans earlier this week.
But there are a few key differences. Most importantly, Moderna's vaccine can be stored in normal freezers and does not require a super-cold transportation network, making it more accessible for smaller facilities and local communities.
The US Food and Drug Administration plans to grant emergency use authorization to Moderna for the vaccine, FDA Commissioner Dr. Stephen Hahn and Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, said in a statement Thursday night.
That's after the FDA's vaccine advisory committee made its recommendation for the vaccine Thursday. The FDA's final decision is expected by Friday.
Here's a look at what we know about the Moderna vaccine and how it compares to Pfizer's.
While Pfizer is a pharmaceutical behemoth, Moderna -- short for modified RNA -- is a biotech company based in Cambridge, Massachusetts.
Established in 2010, Moderna has never brought a product to market, or gotten any of its nine or so vaccine candidates approved for use by the FDA. It had also never brought a product to phase three of a clinical trial previously.
The company's scientists had already been collaborating with researchers from the National Institutes of Health on a vaccine for another coronavirus, Middle Eastern Respiratory Syndrome (MERS). When Chinese researchers released the genomic sequence for the novel coronavirus in mid-January, they had a jump start.
The vaccine, called mRNA-1273, had development help from the National Institute of Allergy and Infectious Diseases. The US Biomedical Advance Research and Development Authority, known as BARDA, supported late-stage clinical trials and has helped scale up manufacturing.
The FDA green-lit clinical trials of Moderna's vaccine on March 3, the first out of the gate. Its advanced stage clinical trial started July 27 and it was the first government-funded Phase 3 clinical trial for a Covid-19 vaccine in the US. The company applied to the FDA for emergency use authorization for the vaccine on November 30.
In Moderna's trial, 15,000 study participants were given a placebo, which is a shot of saline that has no effect. Over several months, 185 of them developed Covid-19, with 30 developing severe forms of the disease. One of them died.
Another 15,000 participants were given the vaccine, and only 11 of them developed Covid-19. None of the 11 became severely ill.
The vaccine was effective across age groups, genders, racial and ethnic groups, and participants with medical comorbidities associated with high risk of severe Covid-19, according to the briefing document. About 10% of study participants were Black and 20% were of Hispanic or Latino.
How does it work?
Like Pfizer's vaccine, Moderna's delivers messenger RNA, or mRNA, which is a genetic recipe for making a piece of the spikes that sit atop the coronavirus. Once injected, the body's immune system makes antibodies to the spikes. If a vaccinated person is later exposed to the coronavirus, those antibodies should stand at the ready to attack the virus.
The Moderna vaccine in particular contains a synthetic mRNA that codes for a structure called the "pre-fusion stabilized spike glycoprotein" of the virus.
The vaccine also contains fatty materials called lipids, tromethamine, tromethamine hydrochloride, acetic acid, sodium acetate and sucrose.
How is Moderna's vaccine different from Pfizer's?
The two vaccines are very similar, but they have a few key differences that make Moderna's vaccine "more flexible," as US Health and Human Services Secretary Alex Azar said last month.
Efficacy: Both Moderna's and the Pfizer-BioNTech vaccine have shown similar efficacy levels of near 95%.
"They appear to be roughly equivalent," said Dr. Paul Offit, a member of the FDA's vaccine advisory committee, during an appearance on CNN's "New Day" on Tuesday.
"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."
Cold storage: Most importantly, Moderna's vaccine does not need to be kept at super-cold temperatures, like Pfizer's.
The Pfizer vaccine needs to be stored at about minus-75 degrees Celsius, about 50 degrees colder than any vaccine currently used in the US. The vaccine can be put in the refrigerator for only up to five days before it expires.
To accommodate that, the CDC created a complex set of handling and storage requirements known as the "cold chain" that included expensive ultra-cold freezers and lots of dry ice.
In contrast, Moderna's vaccine can be kept at about minus-20 degrees Celsius, or about the temperature of a home freezer, according to Moncef Slaoui, the head of the US effort to develop a vaccine for Covid-19. Moderna's vaccine can also be kept in a refrigerator for 30 days before it expires.
"So that's more manageable and much more commonly available," Slaoui said Tuesday.
These differences suggest that Pfizer's vaccine may be used more for major institutions with established infrastructure like hospitals, while Moderna's may be more useful to smaller facilities like a local chain or pharmacist.
Dosage and timing: Moderna's vaccine is administered as two 100-microgram doses given 28 days apart. Pfizer's vaccine is administered as two 30-microgram doses given 21 days apart.
Age: If authorized, the Moderna vaccine would be used in people 18 and older, while the Pfizer vaccine was authorized for people 16 and older.
To Read More: https://edition.cnn.com/2020/12/17/health/moderna-vaccine-what-we-know/index.html
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