In auto racing, cars sometimes have to make pit stops for potential mechanical problems to be checked out. We're seeing the equivalent of that happen now in the race to develop a coronavirus vaccine.

On Wednesday, AstraZeneca (NYSE:AZN) announced that it was pausing late-stage clinical trials of COVID-19 vaccine candidate AZD1222. Why? A participant in the U.K. trial experienced an unexplained illness after receiving the investigational vaccine.

The pause didn't last long. On Saturday, AstraZeneca received a green light from U.K. regulators to resume the clinical trial. However, as pit stops do with car racing, this temporary delay changes the dynamics in the coronavirus vaccine race to some extent. And I think that there's one surefire vaccine winner following AstraZeneca's COVID-19 trial pause -- Pfizer (NYSE:PFE).

Scientist holding COVID-19 vaccine bottle with one hand and giving a thumbs-up with the other hand

Image source: Getty Images.

What it doesn't mean

Before my use of the term "surefire winner" causes a surefire firestorm, allow me to provide some context. I'm not in any way implying that Pfizer and its partner BioNTech (NASDAQ:BNTX) are guaranteed success with their COVID-19 vaccine candidate BNT162b2.

Granted, I think the chances of success for BNT162b2 are pretty good. I base my view on the clinical results that have been announced so far and the historical track record of vaccines that make it to phase 3 testing. Between 2006 and 2015, over 74% of vaccines in phase 3 testing went on to win FDA approval, according to industry organization BIO. But I also realize that there's a real possibility that Pfizer's and BioNTech's vaccine could stumble in late-stage testing. 

I also don't mean that Pfizer will necessarily be the best-performing stock out of all of the companies developing COVID-19 vaccines because of AstraZeneca's delay. Smaller biotech stocks could (and probably will) deliver greater returns than Pfizer will. 

Winning the perception game

So what do I mean when I maintain that Pfizer is the "surefire winner" after AstraZeneca's COVID-19 clinical trial pause? The big drugmaker is now viewed as the clear frontrunner in the coronavirus vaccine race by many investors. Pfizer is winning the perception game.

To be clear, I don't think the trial pause will hurt AstraZeneca all that much over the long run. After all, it lasted only a few days. But to return to the car race analogy, AstraZeneca's "pit stop" is allowing another drugmaker to move into a clear lead in the race.

Why isn't Moderna (NASDAQ:MRNA) that clear leader? Just a few days before AstraZeneca's announcement of its trial pause, the biotech revealed that it's temporarily slowing down enrollment in the late-stage study of COVID-19 vaccine candidate mRNA-1273 to boost minority participation. That's a wise move, but the combination of Moderna's slowdown and AstraZeneca's delay works to Pfizer's advantage when it comes to investors' perception.

There are other companies with coronavirus vaccine candidates already in late-stage testing. But they're based in China and Russia. Their vaccines are likely to be non-factors in the U.S. market. Johnson & Johnson (NYSE:JNJ) also is starting late-stage testing of its COVID-19 vaccine this month. However promising this vaccine might be, though, J&J lags well behind Pfizer.

BioNTech arguably deserves greater acclaim than Pfizer. After all, the German biotech originally developed multiple coronavirus vaccine candidates, including BNT162b2. But Pfizer recognized the potential for the BNT162 program and ponied upfront cash to fund the development of the investigational vaccines. A lot more U.S. investors know who Pfizer is than know who BioNTech is. Again, it's all about perception.

Will Pfizer be the ultimate winner?

There's no question in my mind that Pfizer is the clear winner from AstraZeneca's trial delay -- for now. But will the big pharma company be the ultimate winner in the coronavirus vaccine market? That remains to be seen.

I definitely think Pfizer could be the biggest winner over the long run in terms of global sales. It's a positive sign, in my view, that the company plans to advance another COVID-19 vaccine candidate into early stage clinical testing in September. That shows that Pfizer is looking to the future and not just the near term.

But there's also a surefire certainty: The coronavirus vaccine race is far from over.