We could be only days away from the first two emergency use authorizations (EUA) for COVID-19 vaccines in the U.S. An FDA advisory committee meets on Thursday to review the EUA filing for BNT162b2, the vaccine candidate developed by Pfizer (NYSE:PFE) and BioNTech (NASDAQ:BNTX). One week later, this same advisory committee reconvenes to review Moderna's (NASDAQ:MRNA) EUA submission for mRNA-1273.

Pfizer/BioNTech and Moderna have large supply deals lined up with the U.S. and other governments. Their vaccines are likely to rake in well over $10 billion each in 2021 alone. Some expect that Pfizer and BioNTech will edge out Moderna in overall sales. However, here's what could make Moderna's COVID vaccine a bigger winner than BNT162b2. 

A magnifying glass held in front of two COVID-19 vaccine vials with a $100 bill behind them

Image source: Getty Images.

A severe advantage

Both Pfizer's and Moderna's coronavirus vaccines achieved exceptionally high efficacy levels. Pfizer and BioNTech reported 95% efficacy for BNT162b2. Moderna's reported efficacy for mRNA-1273 was only a little lower at 94.1%. 

There was one piece of data in Moderna's late-stage results that just might give it an advantage over BNT162b2. The biotech said that there were 30 severe cases of COVID-19 observed in its clinical study. All of those cases occurred in the group of participants receiving placebo with none in the group receiving mRNA-1273.

Pfizer and BioNTech announced that 10 severe cases of COVID-19 were observed in its late-stage study. Nine of those occurred in the placebo group with one in the group vaccinated with BNT162b2.

Moderna CEO Stephane Bancel said in an interview with CNBC that the results showing 100% protection from severe cases of COVID-19 was "the most exciting news" his company announced from the late-stage data. He's arguably right. These results could make Moderna's coronavirus vaccine more attractive for administering to high-risk individuals than Pfizer's and BioNTech's vaccine. 

Getting warmer

The cold-storage requirements for Pfizer's and BioNTech's COVID vaccine have received a lot of attention in the press. BNT162b2 must be stored at minus 94 degrees Fahrenheit, a lot colder temperature than standard freezers support.

Pfizer and BioNTech designed special thermal shippers filled with dry ice that maintain the needed temperature. These shippers can be used as temporary storage units for up to 15 days by refilling with more dry ice as needed.

Moderna's mRNA-1273 is a messenger RNA (mRNA) vaccine like BNT162b2. It also initially required ultracold storage. However, Moderna modified its approach to address this issue. Its coronavirus vaccine can now remain stable at temperatures between 36 degrees and 46 degrees Fahrenheit for 30 days. This means that standard refrigerators can be used to store mRNA-1273. The vaccine also will remain stable at minus four degrees Fahrenheit for up to six months and at room temperature for up to 12 hours. 

The cold-storage advantage for Moderna might not be a huge factor right out of the gate in the U.S. and in other wealthy nations. Physicians' offices and smaller pharmacies that will soon seek to provide COVID-19 vaccinations probably won't be eager to invest in the freezers currently required for BNT162b2, though. Developing nations also aren't likely to be able to afford the higher costs of this cold-storage equipment.

Pfizer has indicated that it's developing a freeze-dried version of BNT162b2 that won't require ultracold storage. It's possible that this version of the vaccine will be available sometime next year. If not, the company's COVID vaccine could remain at a disadvantage compared to Moderna's vaccine.

Another winning front

There's also another front where Moderna's COVID-19 vaccine is likely to be a bigger winner than BNT162b2 will be for Pfizer: Boosting its maker's stock price. Success for mRNA-1273 will have a much greater impact on Moderna's financial position than BNT162b2 will have for Pfizer. As a result, the biotech stock seems likely to deliver larger gains than Pfizer over the next few months.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.