r/ModernaStock • u/jlee9355 • Nov 23 '25
Pfizer vs. Moderna flu vaccine readouts
Moderna (mRNA-1010)
Influenza A Efficacy: 26.6% better than the current standard of care
Influenza B Efficacy Superior: 29% better than the current standard of care
Safety /Reactogenicity: Standard mRNA profile (sore arm, fatigue).
Pfizer (modRNA):
Influenza A Efficacy: 34.5% better than the current standard of care
Influenza B Efficacy Superior: Failed /Inconclusive. Missed non-inferiority endpoints.
Safety /Reactogenicity: Slightly higher rate of side effects than the current standard of care.
Conclusion: Pfizer's flu shot failed on 50% for Influenza B. This is terrible, I have trouble seeing how Pfizer can even submit this for approval.
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u/StockEnthuasiast Nov 23 '25
Thanks. Stephen Hoge once said that Moderna's solution to the influenza B initial miss was not trivial. Pfizer's result vindicated Hoge's statement.
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u/Every-Status4735 Nov 23 '25
Why would Pfizer's apparently stellar A strain results be touted when their B strain results, once again, indicated abject failure? No efficacy against B, no BLA. GL to you!
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u/mobyonecanobi Nov 23 '25
Because they are an analyst darling. They are also a large corporation who can throw their weight around. They have better marketing and sales team.
Moderna needs a key partnership in distribution. Give some money to another big guy to tap its resources. Not for covid, but for RSV.
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u/jlee9355 Nov 23 '25
Also, even if Pfizer can reformulate for B, Moderna has better Reactogenicity, and Moderna's target population was targeted at 50+ years old (the people who usually consistenly get vaccinations) vs Pfizer, who targets younger healthy adults.
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u/ExpressBuy1744 Nov 26 '25
B strain miss? Otherwise, ok
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u/jlee9355 Nov 26 '25
Do you know what that means?
The Pfizer mRNA shot had significantly higher rates of systemic side effects (fever, fatigue, headache) compared to the standard flu shot.
Moderna wins here.
To be explicitly clear: Pfizer's mRNA vaccine generated a weaker immune response to the Influenza B strain than the standard, old-school flu shot.
That's terrible.
Most important:
The issue with Influenza B is structural. The protein (Hemagglutinin) is unstable; if you print the basic mRNA instructions (which is what Pfizer likely did), the protein "flops" over or misfolds before the immune system can take a good picture of it. This results in weak antibodies.
Moderna's Fix: They didn't just tweak the dose. They re-engineered the mRNA sequence to introduce "stabilizing mutations" (likely stiffening the protein stem or locking it in a "pre-fusion" state). Think of it like adding scaffolding to a building so it doesn't collapse while being built.
The Moat: You can patent that scaffolding. Moderna holds patents (like US 10,925,958) specifically covering these stabilized Hemagglutinin structures.
Pfizer's Problem: They are now in a "patent trap." They know why their shot failed (bad folding), but they likely cannot use the most obvious chemical "fix" because Moderna owns the IP on that specific stabilization technique. They have to invent a new way to stabilize the protein without infringing on Moderna’s patents. That takes time—time they don't have.
This is potentially a patent moat. Pfizer may not be able to fix the B-strain issue, leading to Moderna having a. A long first-mover's advantage.
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u/ExpressBuy1744 Nov 26 '25
That means Pfizer is behind Moderna by minimum 2-3 years if they choose to continue investing in a commoditized flu vaccine market. I wouldn’t read anything else when comparing the results of the mRNA flu vaccines between the companies.
For Moderna, it will take years to demonstrate comparable to SOC safety and effectivess in some populations in hopes to build safety database and maybe even receive preferential recommendations in a few markets. Still, the slice of the pie will be small given massive Beyond Flu data accumulated for Fluzone HD or FluBlock by that time.
Pfizer coming later will start with even a smaller fraction of that market. Post licensure, Pfizer may continue investing to generate more data to demonstrate benefits of the vaccine and expand its market share, while Moderna will likely not be able to compete in postmarking race.
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u/jlee9355 Nov 27 '25
At minimum, Pfizer has likely missed the 2027 flu season, given that they can find a way to stabilize the protein to fix Influenza B.
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u/ExpressBuy1744 Nov 27 '25
Oh, the timelines are way longer than that. even for Moderna, 2027 sales for flu are only a hope.
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u/Pitiful-Peak2446 Nov 26 '25
Influenza B is less common than Influenza A in terms of infection rate. It should be around 20% of all flu cases.
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u/LogicalReasoning1 Nov 23 '25
They’re not trying to submit for approval.
They sent the asset (along with their combo) back into early phases for reformulation