This vaccine is first of it's kind, an mRNA vaccine, which is pretty cool. I'm sure this will revolutionize how vaccines are made in the future.
They chose the spike protein as the target of their vaccine, which is what the virus uses to penetrate cells and the main antigenic component that induces immune responses.
So mRNA codes proteins. This little strand mRNA they're using just codes the spike protein of the virus. So it's coated in this lipid barrier which is protecting the mRNA, gets it into cells, gets transcribed into this spike protein, and then the presence of this protein triggers an immune response against the spike protein.
They basically just need this little piece of mRNA and a vehicle to get it in the cell. Sounds simple, but it had never been done before in humans.
90% is super good. I think that is better than what they were probably hoping for. Still tons of questions to answer, including how long it lasts, safety issues, and subgroup analysis.
Another issue that people aren't talking much about is how this is going to get distributed. They say half a billion doses before end of the year, and Trump said something about the military or something. But these vaccines will have to be kept at cold temperatures. I think distribution will be a problem, especially in more rural areas.
Moderna is also mRNA and has been in development for 8 years. It was originally commissioned to fight MERS. Since both are coronavirus and since mRNA vaccines only create the protein spike it was easy to shift quickly to COVID.