modRNA
Nucleoside-modified RNA.
The COVID-19 mRNA vaccines made by Pfizer-BioNTech and Moderna are referred to in regulatory documents as
“nucleoside modified RNA” (modRNA) vaccines because the uridine residues have been replaced with N1-
methylpseudouridine (1-methylΨ).
This substitution allows the modRNA to evade normal defense mechanisms that detect foreign RNA allowing the vaccinal RNA to enter the cell, ultimately to produce spike protein.
The discovery of this fact led to the award of the Nobel Prize in Physiology and Medicine in 2023 to Katalin Karikó and Drew Weissman.