Pfizer (PFE -0.43%) continues to rake in billions of dollars in sales for its messenger RNA (mRNA) COVID-19 vaccine developed with BioNTech (BNTX -4.08%). However, the big drugmaker has bigger plans for its mRNA vaccine program. In this Motley Fool Live video recorded on Sept. 29, Motley Fool contributors Keith Speights and Brian Orelli discuss Pfizer's next mRNA vaccine candidate.

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Keith Speights: Pfizer, PFE is the ticker there, announced on Monday that it has begun a phase 1 study of a messenger RNA flu vaccine in adults. Of course, Pfizer and its partner BioNTech, already have massive success with their COVID-19 vaccine.

But what do you think of Pfizer's prospects with this flu vaccine program? How much is Pfizer behind Moderna (MRNA -3.58%) in the race to develop an mRNA flu vaccine?

Brian Orelli: Moderna dosed its first patient in the beginning of July, it has almost a three-month headstart. But the companies are taking completely different pathways to their first in-human clinical trials. Moderna is testing three dose levels of its vaccine that's designed to protect against four different strains of influenza and it's comparing that to placebo.

Presumably, it will actually be able to get some efficacy data from the study. Although it's only 180 patients and it's going to measure safety and antibody levels as well. That's probably, a majority of the information will come from there. But presumably, because they have a placebo in the group, they can actually measure whether it's keeping people from getting influenza.

Although, as I said, it's a small number. Maybe they don't get enough data to actually get the statistical significance.

Pfizer's taking a completely different approach. They're also trying to get a four-quadrant vaccine that covers four different strains of influenza. But they're going to test it individually. They're going to test four different dose levels of one strain that contains influenza A, and then four different dose levels of one strain that contains Influenza B. Then they're going to mix those two.

They're going to test four different dose levels of vaccine that contains one A and one B. Then they're going to go on and test the quad, just two As and two Bs. Then they're going to compare all of that to a quad that's already approved and a flu vaccine that's already approved. They're going to look at antibody levels and safety and compare all those different potentials. Hopefully, the quad works the best.

Then compare that to an active comparator. They won't be able to get any efficacy data obviously because they don't have placebo control. But as you can imagine, that's going to take a lot more people and they need 615 participants. Then everyone who got the experimental vaccine is also going to get the approved vaccine eight weeks later. Definitely, there's not even very much time to actually see that there isn't any flu in the experimental arm.

I really don't think we're going to get any efficacy data from Pfizer's clinical trial. I suspect that the difference is that Moderna might have a better handle on the safety components of their vaccine. Pfizer is new to this. Obviously, they've worked with BioNTech with the COVID-19. But presumably, if they're the complete owners of this flu vaccine, then they're not using any of that TAC. It's basically brand new. Maybe that's why they have to go slower than Moderna is able to do.

Speights: I was reading Pfizer's press release on this and they did mention BioNTech at the very end of the press release. I think this was the program Pfizer was working with BioNTech on before COVID 19 came along.

This isn't a deal where they'll be splitting anything with BioNTech. BioNTech just gets some royalties if everything goes well.

But yeah, Pfizer is still using some of what BioNTech developed, but I think this is the company's first step more on its own in the mRNA world. But yeah, it's clearly a few months behind Moderna.

Both of these companies are behind another COVID-19 vaccine maker that has a promising flu vaccine, Novavax (NVAX -4.32%). Novavax of course, it's not in a messenger RNA vaccine, but Novavax has a promising flu vaccine as well called NanoFlu.

Orelli: Of course, there's a lot of flu vaccines already on the market, so it's not exactly a super lucrative business just because there's so many different options that pharmacists have to buy different versions of the vaccine that should potentially do exactly the same thing. It's hard to differentiate here.

Speights: Maybe the best shot, no pun intended, is that multiple of these vaccines maybe could be just a lot more effective against the flu. We'll see.

Orelli: Yeah, maybe.

Speights: Yeah, maybe.

Orelli: I think the problem with the flu vaccine is probably more has to do with the inability for us to be able to predict which flu is actually going to be circulating. They guess based on the Southern Hemisphere, that that's how they decide what four or three or four are they going to put into the vaccine in the Northern Hemisphere.

If they guess wrong then the vaccine isn't very effective, and if they guess right then it is quite effective. I think that has more to do with the effectiveness of the current vaccines than that they just don't produce antibodies very well. I think that that's probably not going to change a whole lot when you could've went mRNA.

Although in theory, it might be easier to add more. You might be able to go to six or eight strains or something like that.

Speights: With the mRNA vaccines?

Orelli: Yeah, exactly. Just because it was basically just synthesizing under the mRNA and stick it in the delivery, but envelope bubble thing that attaches to the cell. I think that it may not be that difficult. Although, at some point, you got to endure expression level. If you're diluting it out, now you don't have as many mRNAs, so you may not get as much of an expression.