The Nobel Prize in Physiology or Medicine was awarded for discovering use of Pseudouridine to suppress immune responses to synthetic mRNA, and use of that discovery in COVID-19 mRNA vaccines.

Background
Natural RNA, including mRNA, consists of a polymerized string of four different compounds – A, U, G, C. U = Uridine. There are many different natural forms of RNA in cells, but in general, DNA makes mRNA, and mRNA makes protein (polypeptide).

In cells after polymerization, in some mRNA there are precisely controlled modifications to the “U” compounds (bases) to convert them to a different compound, called pseudouridine. The presence of such precise pseudouridine modifications regulate many aspects of mRNA biology, including how long it persists in the cell before being degraded, the structures that it forms when folding, how efficiently it is turned into protein (translated), and the activity of certain cell types containing this modified mRNA when responding to inflammation. Pseudouridine messages an anti-inflammatory (which is to say immunosuppressive) signal to cells.

Kariko and Weissman recently received the Nobel Prize in Physiology or Medicine for their their discovery that replacement of synthetic pseudouridine for uridine throughout synthetic mRNA reduces the inflammation triggered when this synthetic mRNA is delivered into the cells of animals using self-assembling cationic lipid delivery particles, and specifically the use of that discovery to enable the rapid development of the Pfizer/BioNTech and Moderna COVID-19 mRNA “vaccines” that have been deployed throughout the world.