Moderna, the producers of the mRNA-1273/Spikevax vaccine, are the ones principally responsible for the development of the mRNA transfection tech currently used in various COVID-19 vaccines.

The seed of the idea that would germinate into Moderna was planted in 2005, when Derrick Rossi read a paper written by Hungarian scientist Katalin Karikó on how nucleoside-modified mRNA could be made to evade human immune responses from toll-like receptors.

The paper in question was published in Cell, back in 2005:

Cell – Suppression of RNA Recognition by Toll-like Receptors: The Impact of Nucleoside Modification and the Evolutionary Origin of RNA

According to this paper, using pseudouridine in place of uridine allows foreign mRNA to escape detection by TLR7/8.

Toll-like receptors are a type of PRR, or pattern-recognition receptor, the smoke alarms of human (and other mammalian) cells. Their purpose is to detect molecular signs of damage or foreign objects (DAMPs and PAMPs) and induce an inflammatory response.

Frontiers – Toll-like receptor signaling pathways

The innate immune system employs germline-encoded pattern-recognition receptors (PRRs) for the initial detection of microbes. PRRs recognize microbe-specific molecular signatures known as pathogen-associated molecular patterns (PAMPs) and self-derived molecules derived from damaged cells, referred as damage-associated molecules patterns (DAMPs). PRRs activate downstream signaling pathways that lead to the induction of innate immune responses by producing inflammatory cytokines, type I interferon (IFN), and other mediators. These processes not only trigger immediate host defensive responses such as inflammation, but also prime and orchestrate antigen-specific adaptive immune responses (1). These responses are essential for the clearance of infecting microbes as well as crucial for the consequent instruction of antigen-specific adaptive immune responses.