No matter how you look at it, Pfizer (PFE 0.23%) has had a remarkable year in 2020. The big drugmaker made a critical decision early on to team up with German biotech BioNTech (BNTX 0.55%) on developing a COVID-19 vaccine. That decision has paid off, with Pfizer and BioNTech becoming the first coronavirus-vaccine makers to win emergency use authorization (EUA) in the U.S.

Pfizer stock generated double-digit percentage gains over the last month as investors' enthusiasm about its coronavirus vaccine rose. However, those gains have now all but evaporated. Is Pfizer's COVID vaccine growth story already over?

Typewriter with a paper containing only the words End of story...

Image source: Getty Images.

Why the answer could be "yes"

For a few days, Pfizer's and BioNTech's BNT162b2 was the only coronavirus vaccine on the market in the U.S. That monopoly was short-lived. Last Friday, the U.S. Food and Drug Administration (FDA) granted EUA to Moderna's (MRNA 3.28%) mRNA-1273.

Both BNT162b2 and mRNA-1273 were found to be safe and highly effective. However, Moderna could give Pfizer a run for its money because its COVID-19 vaccine doesn't have the ultracold storage requirements that BNT162b2 does.

But that's not the biggest reason to think that Pfizer's COVID vaccine growth story could be over. An even more formidable rival vaccine could be on the way.Johnson & Johnson (JNJ 0.29%) expects to announce results from a late-stage study of its coronavirus vaccine JNJ-78436735 next month. If those results are positive, J&J could win EUA for its vaccine by February.

Unlike BNT162b2 (and all of the other leading coronavirus vaccines), J&J's vaccine requires only a single dose. It doesn't have any ultracold storage requirements. What's more, the healthcare giant has committed to selling JNJ-78436735 at cost during the pandemic.

Could investors have looked at the potential landscape in 2021 and decided not to bank on growth for Pfizer's COVID-19 vaccine beyond the supply deals the company has already lined up? It's possible.

Don't be too certain

There's an old saying that you shouldn't put the cart before the horse. That adage is definitely applicable in any discussion of Pfizer's prospects for its coronavirus vaccine.

It's simply too early to know if J&J's vaccine will stack up well against BNT162b2. Johnson & Johnson has modeled for 70% efficacy but hopes to achieve a higher level. But if the efficacy for JNJ-78436735 turns out to be in the ballpark of 70% or less, developed nations like the U.S. could prefer to boost their orders for Pfizer's vaccine rather than go with a lower-efficacy alternative.

What about the ultracold storage limitation for BNT162b2? Pfizer hopes to address that issue by sometime next year. The company is working with BioNTech to develop a lyophilized (freeze-dried) version of BNT162b2 that wouldn't require ultracold storage. Pfizer's chief scientific officer Mikael Dolsten thinks this new and improved version could be ready to go in 2021.

Don't overlook Pfizer's head start for its vaccine in minors. The company won EUA for BNT162b2 in vaccinating individuals age 16 and up. Moderna's EUA only applies to individuals age 18 and older. Pfizer also began testing its vaccine in adolescents age 12 and older before any of its rivals.

There's a good case to be made that none of Pfizer's growth prospects for BNT162b2 are priced into its shares. The big pharma stock is basically at the same price where it started 2020. However, Pfizer stands to make $14 billion from its COVID vaccine next year that wasn't even on the table at the beginning of this year.

A bigger story

Most importantly, though, Pfizer's story is much bigger than just its coronavirus vaccine. The recent transaction that merged its Upjohn subsidiary with Mylan will change Pfizer's future prospects considerably.

Pfizer expects to generate average adjusted earnings-per-share growth of around 10% over the next several years -- even without contributions from BNT162b2. That kind of growth, combined with Pfizer's solid dividend, should be enough to give investors attractive total returns.

Of course, Pfizer will definitely make a significant amount of money from BNT162b2 over the next few years. That will be true regardless of how J&J's vaccine fares in late-stage testing. The growth story for Pfizer's COVID vaccine isn't over; it's just beginning. And the overall growth story for Pfizer looks better than it's been in a long time.