This week, Moderna (NASDAQ:MRNA) took another step toward the finish line in the coronavirus vaccine race. On Monday, the biotech company applied for Emergency Use Authorization (EUA) for its investigational vaccine. The move follows the submission by rival team Pfizer (NYSE:PFE) and BioNTech (NASDAQ:BNTX) ten days earlier.

Moderna said its vaccine candidate was well tolerated. And efficacy, at 94.1%, was well above the 50% bar set by the U.S. Food and Drug Administration (FDA). But that metric might have disappointed some.

Efficacy after the company's first interim review of the trial was at 94.5%. So efficacy declined, albeit slightly, as coronavirus cases accrued. Pfizer's efficacy increased from the first review to the second -- from 90% to 95%. Should we be worried about Moderna? And does this give Pfizer an edge?

An investor holds her head while examining company data on her computer.

Image source: Getty Images.

A look at the numbers

First, let's take a closer look at the numbers. Moderna's and Pfizer's trials included 30,000 and 43,000 people, respectively. Each participant was given either the investigational vaccine or placebo.

Moderna reported 95 cases of coronavirus after its first review. Five were in the vaccinated group, and 90 were in the placebo group. The second review included 196 cases -- 185 occurred in the placebo group and 11 were in the vaccinated group.

In Pfizer's first review, the company reported 94 coronavirus cases and 90% efficacy of its vaccine candidate. It didn't offer further details. In the second review, it said efficacy had reached 95%. At that point, Pfizer said that of 170 coronavirus cases, 162 occurred in the placebo group and eight in those who'd received the investigational vaccine.

For Moderna, vaccinated participants represent 5.6% of the total number of coronavirus cases. And for Pfizer, vaccinated participants make up 4.7% of the total cases.

Right now, this isn't particularly worrisome for Moderna or its investors. It's normal for data to shift one way or the other as more and more coronavirus cases build up during a trial. When a movement remains minor -- for instance, within a percent or two -- we shouldn't be concerned. But it's something to keep an eye on if Moderna reports further confirmed coronavirus cases among participants. The company plans on collecting follow-up data on participants over a two-year period.

Surpassing Pfizer

Still, it's fair to say that on overall efficacy, Pfizer is a step ahead. But here's where Moderna's candidate surpasses that of Pfizer: So far, it's better at preventing severe disease. In Pfizer's trial, one vaccinated individual developed a severe case of COVID-19; none of the Moderna-vaccinated volunteers developed severe cases.

This could be a big advantage, and here's why. Severe coronavirus cases are the most worrisome, leading to overwhelmed healthcare systems and poor patient outcomes. If rivals' product candidates aren't 100% efficacious here and Moderna continues to be 100% efficacious, the biotech could score a major win. This efficacy in preventing severe illness could make Moderna a leader -- or the leader -- in the coronavirus vaccine market.

Trial Data on Final Analysis Moderna Pfizer
Total COVID-19 cases 196 170
Cases in placebo group 185 162
Cases in vaccinated group 11 8
Severe cases in vaccinated group 0

Data Source: Company reports. Table by author.

So what does all of this mean for investors? Should you favor shares of Moderna over Pfizer?

If you're an aggressive investor looking for share-growth potential, the answer is yes. Pfizer has a vast array of marketed products, so revenue from just one would be less of a growth driver than it would be for Moderna. The biotech doesn't yet have a commercialized product.

There is risk, of course -- for Moderna and its rivals. New efficacy or safety issues could arise as researchers follow up with trial participants. Or the FDA might reject the vaccine candidate based on details that haven't been made public to us.

But according to data Moderna has publicly reported, the biotech's situation looks positive. It seems likely the FDA will authorize the vaccine for emergency use, and maybe even as soon as this month.

I wouldn't be bothered by slight shifts in data, especially if Moderna's vaccine candidate continues to prove it can thwart the very worst cases of COVID-19.

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.