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Why experts say Moderna vaccine holds advantage over Pfizer's candidate


Karen Bouffard   | The Detroit News

The mRNA-based coronavirus vaccine developed by Moderna Inc. and vetted in clinical trials at the Detroit-based Henry Ford Health System is based on the same technology used by Pfizer Inc. to develop its vaccine candidate, but would not have the same requirement for storage at ultra-cold temperatures. 

Pfizer and Moderna are the first companies to release partial results from Phase 3 clinical trials in the race to develop a vaccine against the deadly SARS-CoV-3 virus that causes COVID-19.  

Moderna said Monday its vaccine was found to be 94.5% effective in initial results. Pfizer's candidate was found to be 90% effective in initial results made public on Nov. 9.

Pfizer and Moderna both have developed two-dose vaccines that would be the first vaccines ever to be based on mRNA, or messenger RNA technology.

Although Pfizer's vaccine must be stored in ultra-cold temperatures — about -112 degrees Fahrenheit, according to the company — Moderna's vaccine can be stored in a regular refrigerator. 

"The (Moderna) vaccine has a refrigerator storage temperature," Dr. Paul Kilgore, the senior investigative leader for the Moderna trial at Henry Ford Health System, said during a Monday media briefing. "It also is stable at room temperature for a few hours, so it has some major advantages."

The ability to store the vaccine in a regular freezer would be a boon for distribution of the vaccine, said Tinglong Dai, an associate professor of operations management and  business analytics at Johns Hopkins University and an expert on health care supply chain issues. 

"If this Moderna vaccine is actually proven to be successful, it would definitely be a game-changer in terms of health care supply chain," Dai said, noting that the Moderna vaccine could be stored in a regular refrigerator for up to 30 days after thawing and would last for six months if frozen. 

"It can be kept at regular room temperature for up to 12 hours," he added. 

With conventional vaccines, a piece of inactivated virus, called an antigen, is injected into the body, where it's recognized as a toxin or foreign body. That triggers the body's immune system to produce specific antibodies to fight the invader and prepare for the next time it encounters the pathogen. 

With the Pfizer and Moderna vaccines, messenger RNA is injected into the body, where it enters the cells and provides instructions to make antigens. When the cell presents the antigens to the body's immune system, that triggers the production of T-cells and antibodies to fight the infection. 

The mRNA is encased in a lipid nanoparticle that helps it remain stable, Henry Ford Health's Kilgore said. Different formulations of the two company's lipid nanoparticles could partly explain why Moderna's vaccine can be stored at a higher temperature than Pfizer's, he noted. 

And Moderna's lipid nanoparticles contain more mRNA than in the Pfizer vaccine, Kilgore added.

"The content of the mRNA in the Moderna vaccine is 100 micrograms. In the Phase 3 trial for Pfizer, the concentration is lower, around 30 micrograms." Kilgore said. "That may also mean, when you have higher concentrations in lipid nanoparticle, you have more mRNA that stays around, even at a higher temperature.

"Because there's only 30 micrograms in the Pfizer mRNA vaccine it's really critical that those micrograms remain intact." 

Pfizer expects to produce up to 50 million vaccine doses by the end of this year and up to 1.3 billion doses in 2021 between its Kalamazoo manufacturing operation and a Puurs, Belgium, plant tagged to provide the European supply. 

The New York-based company has designed and built specialized equipment including a 350-unit ultra-low-temperature "freezer farm" on its Kalamazoo campus to store the COVID-19 vaccine at -112 degrees Fahrenheit. The product will be packed in dry ice for shipping. 

Michigan and other states have been tallying their capacity for ultra-cold storage and purchasing ultra-cold freezers in anticipation of the Pfizer vaccine.

"We have surveyed providers and are aware of about 50 ultra-cold freezers in Michigan. We also purchased nine freezers, which will be available regionally across the state," Michigan Department of Health and Human Services spokeswoman Lynn Sutfin told the Detroit News last week. 

Melanie Ivarsson, chief development officer for Moderna, said the company has begun preparing the documentation required to apply for emergency use authorization from the federal Food and Drug Administration and is manufacturing the vaccine in the meantime.

If the emergency use authorization application is approved, Moderna will have doses ready to distribute during the month of December, Ivarsson said.

"This definitely has huge implications for how we're going to (distribute a vaccine) throughout this country and around the world, because very, very few places have ultra-cold freezers," said Dai, the Johns Hopkins supply chain expert. 

"The big unknown is how effective and how safe the vaccine will be on a larger scale, so we still have a lot to see. But this is definitely encouraging."

kbouffard@detroitnews.com

Twitter: @kbouffardDN