We've seen over the past 11 days that Pfizer and Moderna are, without question, the clear leaders in the coronavirus vaccine race. Last week, Pfizer and its partner BioNTech announced great efficacy results for their COVID-19 vaccine candidate BNT162b2. Earlier this week, Moderna followed up with its own fantastic efficacy results for experimental coronavirus vaccine mRNA-1273.

These companies are on track to soon file for U.S. emergency use authorization (EUA). And their chances of winning EUA appear to be quite good. Both BNT162b2 and mRNA-1273 could become available to the first wave of Americans by the end of the year.

While Pfizer and Moderna are the leaders now, that doesn't mean they'll maintain the position indefinitely. Here's the coronavirus vaccine maker that's most likely to blow past both of these drugmakers.

Gloved hand picking up a COVID-19 vaccine bottle from a line of identical bottles.

Image source: Getty Images.

Running close behind

Two companies are running close behind Pfizer and Moderna. AstraZeneca (AZN 0.39%) and Johnson & Johnson (JNJ 0.22%) are also evaluating coronavirus vaccine candidates in late-stage testing in the U.S. 

AstraZeneca expects to announce its late-stage results by the end of 2020. The big drugmaker likely could have reported those results even sooner, but its U.S. study was delayed for a few weeks after a participant in the company's U.K. study of its COVID-19 vaccine experienced an unexplained illness. AstraZeneca's U.S. clinical trial has since resumed.

Johnson & Johnson also had a temporary pause for its late-stage coronavirus vaccine study due to a potential safety issue. An investigation determined that the issue wasn't related to J&J's experimental vaccine, though, and the study moved forward. J&J hasn't indicated when it expects to announce initial results from its late-stage study, although sometime in early 2021 seems likely.

The great efficacy results for Pfizer and Moderna could bode well for both AstraZeneca and J&J. Pfizer's and Moderna's experimental vaccines use modified messenger RNA (mRNA) to instruct the ribosomes in cells to produce proteins that mirror the spike protein on the surface of the novel coronavirus that causes COVID-19. AstraZeneca and J&J use a different approach, where adenoviruses (which are a leading cause of the common cold) deliver DNA that contains instructions for building a copy of the coronavirus spike protein.

In theory, at least, the adenovirus DNA approach could deliver similar efficacy as the mRNA approach used by Pfizer and Moderna. It's too soon to know if that will be the case, though. J&J has stated that it's modeling for 70% efficacy, but thinks the actual level could be higher.

A big sticking point

Which of these coronavirus vaccine makers is most likely to vault ahead of Pfizer and Moderna? I'd go with Johnson & Johnson.

The COVID-19 vaccines developed by Pfizer, Moderna, and AstraZeneca have at least one common denominator: They all require two doses. To be fully vaccinated, individuals must receive the first dose and then get a second dose several weeks later. J&J's coronavirus vaccine candidate, though, requires only one dose.

This could give J&J a significant competitive advantage over its rivals. A single-dose vaccine would have a lower cost than a two-dose regimen. People would also be more likely to want to receive a vaccine that they only have to take once. 

Johnson & Johnson also won't have the ultra-cold storage requirements that Pfizer's vaccine has. Its COVID-19 vaccine can remain stable for up to two years at around minus four degrees Fahrenheit and for up to three months at temperatures between around 35 degrees and 46 degrees Fahrenheit. 

In addition, J&J beats Moderna when it comes to production capacity. Moderna has stated that it will be able to make around 500 million doses of mRNA-1273 next year, although the biotech says that it could "possibly" up that to 1 billion doses. J&J is on track to produce more than 1 billion doses per year.

One thing you shouldn't overlook

I definitely think it's possible that Johnson & Johnson could be more successful with its coronavirus vaccine than Pfizer and Moderna will be with their vaccines. However, note that I never said that the big healthcare stock would outperform either of these two other drug stocks.

My hunch is that the biggest winner of the three in terms of stock performance will be Moderna. Why? It's the smallest of the group. It takes more to move the needle for giant companies like Pfizer and J&J than it does for relatively smaller biotechs like Moderna. The most successful coronavirus vaccine maker on one front might not be (and probably won't be) the most successful on another front.