Pfizer has released Phase 3 data for its mRNA flu vaccine, boasting 34% greater efficacy than the standard flu shot. On paper, this beats Moderna’s candidate, which demonstrated 26.6% efficacy.

If you trade on headlines alone, you buy Pfizer. If you trade on first principles, you recognise the trap.

The trials weren’t even testing the same thing.

The Demographic Divergence: Premium vs. Commodity

Pfizer’s 34.5% victory was achieved exclusively among adults aged 18–64. Moderna’s 26.6% victory, however, came from a massive trial of ~41,000 adults aged $50+, delivering a crucial 27.4% superiority in the 65+ demographic.

The 18–64 bracket is the commodity market. Very few people in this age group die or end up in the ICU from the flu.

The 65+ bracket is the premium market. That’s the group that actually fills hospital beds, racks up billion-dollar Medicare bills, and is the entire reason high-dose shots like Fluzone HD even exist.

Pfizer won the participation-trophy age group. Moderna won the one payer that will pay a premium.

The Influenza B Disaster

Then there’s the Influenza B disaster for Pfizer. This is the part that genuinely shocked me:

Pfizer’s shot was worse than the standard egg-based vaccine against Influenza B strains. Not just “slightly less good”—it missed. There is basically zero chance Pfizer gets this approved as-is.

Moderna faced this exact failure last year. They went back, re-engineered the shot, and the June 2025 data proves they fixed it: 29% greater efficacy against Influenza B.

Why Pfizer is Structurally Screwed

It comes down to structural engineering. The Hemagglutinin protein (the part of the virus the immune system targets) is notoriously unstable. If a company simply prints the basic mRNA instructions (which Pfizer likely did), the protein “flops” or misfolds. The immune system takes a picture of a collapsed building, resulting in weak antibodies.

Moderna didn’t just tweak the dose; they engineered “stabilizing mutations.” Think of it as adding steel scaffolding to the protein so it stands tall in a “pre-fusion” state long enough for the immune system to recognise the correct structure.

The IP Moat

This is the most critical factor: Moderna owns the patent on that scaffolding. US Patent No. 10,925,958 (“Influenza Vaccine”) specifically covers these RNA-encoded, stabilized Hemagglutinin structures.

Pfizer now has to either (a) license it, (b) fight the patent in court, or (c) invent some completely different stabilization method that doesn’t breach Moderna’s claims.

The Investment Thesis: A Strategic Moat

Pfizer’s delay will, at a minimum, miss the 2027 flu season. This ensures Moderna a critical first-mover advantage in the emerging respiratory super-cycle (COVID, Flu, and RSV).

This provides Moderna a clean runway to dominate the premium demographic with a fully validated formulation that works against all four strains, protected by IP that has already survived challenges.

While this development alone doesn’t constitute the ’10-bagger’ moment, it strategically secures Moderna’s position. It creates a robust, defensible business in an evolving market focused on combo COVID/Flu/RSV shots, capable of meeting demand during the next endemic or pandemic.

Crucially, the true value proposition is the robust, validated respiratory vaccine pipeline. This is a foundational step for future platform expansion into latent viruses, oncology, and a wide range of rare diseases. We are likely still very early in realising the full scope of this proprietary mRNA ecosystem.