In the Pfizer and Moderna development programs, researchers replaced 25% of the uracil with pseudouridine.

We revised this check on Nov 7, 2026. See what changed and why ↓

The finding

What remains unresolved

Modified uridine chemistry is well documented, including N1-methylpseudouridine in COVID mRNA products. But the specific development history asserted here, sequential replacement of 25%, then half, then all uracils in the Pfizer and Moderna programs, was not verified. Our first explanation supported only the general chemistry. The Nobel award was in 2023, not the 2022 date later mentioned on air.

Read the supporting source · www.nobelprize.org ↗

Quick answer & review status

Quick answer

Is it true that in the Pfizer and Moderna development programs, researchers replaced 25% of the uracil with pseudouridine?

We can't say yet. Modified uridine chemistry is well documented, including N1-methylpseudouridine in COVID mRNA products. But the specific development history asserted here, sequential replacement of 25%, then half, then all uracils in the Pfizer and Moderna programs, was not verified. Dr. Peter McCullough said it (matched by voice) on Joe Rogan Experience #2576 - Dr. Peter McCullough, aired Nov 4, 2026, at 1:42:26. We couldn't settle it from the evidence we captured, so it stays an open question, not a false claim. The supporting source is nobelprize.org, linked below.

The context belongs here.

No separately verified on-air correction is recorded for this check. That is not a claim that nobody corrected it.

Attribution: Not independently confirmed in this record
Editorial context review: Not recorded; generated finding
Coverage: One selected claim from the episode

Revisions to this check

Nov 7, 2026

Previously: In the Pfizer and Moderna development programs, researchers replaced 25% of the uracil with pseudouridine. [Accurate]: The development of mRNA vaccines for COVID-19 utilized nucleoside-modified mRNA, specifically incorporating N1-methylpseudouridine to replace uracil. This modification was implemented to reduce the immunogenicity of the RNA and increase the stability and translation efficiency of the molecule within host cells.

Now: In the Pfizer and Moderna development programs, researchers replaced 25% of the uracil with pseudouridine. [Unverified]: Modified uridine chemistry is well documented, including N1-methylpseudouridine in COVID mRNA products. But the specific development history asserted here, sequential replacement of 25%, then half, then all uracils in the Pfizer and Moderna programs, was not verified. Our first explanation supported only the general chemistry. The Nobel award was in 2023, not the 2022 date later mentioned on air.

Withdraw an accurate label that validated general chemistry rather than the specific claimed development sequence.

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