It's surprising how buried any mention of pseudouridine is in the wikipedia article's History section [0], when it's clearly a major component of the mRNA story -
7 years of failures [1] before discovering the uridine toxicity problem. Especially considering TFA describes it's
still a point of contention.
[0] https://en.wikipedia.org/wiki/MRNA_vaccine#History
[1] https://www.nytimes.com/2022/01/15/health/mrna-vaccine.html