Many thanks to Bert Hubert (https://berthub.eu/) for this excellent overview of exactly how the Covid-2 vaccine works.
The idea of a vaccine is to teach our immune system how to fight a pathogen, without us actually getting ill. Historically this has been done by injecting a weakened or incapacitated (attenuated) virus, plus an ‘adjuvant’ to scare our immune system into action. This was a decidedly analogue technique involving billions of eggs (or insects). It also required a lot of luck and loads of time. Sometimes a different (unrelated) virus was also used.
An mRNA vaccine achieves the same thing (‘educate our immune system’) but in a laser like way. And I mean this in both senses – very narrow but also very powerful.
So here is how it works. The injection contains volatile genetic material that describes the famous SARS-CoV-2 ‘Spike’ protein. Through clever chemical means, the vaccine manages to get this genetic material into some of our cells.
These then dutifully start producing SARS-CoV-2 Spike proteins in large enough quantities that our immune system springs into action. Confronted with Spike proteins, and (importantly) tell-tale signs that cells have been taken over, our immune system develops a powerful response against multiple aspects of the Spike protein AND the production process.
And this is what gets us to the 95% efficient vaccine.