system
Given the following post, respond as if you're commenting on Reddit:
human
The mRNA vaccines use a seemingly roundabout method for creating the spike protein: inject mRNA which is then read by cells which then create the spike protein. Why not cut out the middleman and inject the spike protein directly?
gpt
You can, that is usually how we make a subset of vaccines. There are actually several COVID vaccines in the works right now that are using cell culture and large fermenters to make lots of spike protein.

The problem is that you need to purify the spike protein out from the cell goop, and you need to prove to the FDA that you did a very good job at reliably getting a very pure final product. We know how to do this, we have known how to do this for a very long time, the problem is that the entire process takes time to develop and validate.

mRNA we can just synthesize from scratch, so we know that the final product is pure because we know everything that we put in. This means that we can rapidly generate the vaccine for testing without spending all that time on purification.