How I understand it, the problem with the first time you're exposed to COVID is that your immune system hasn't seen it before and it takes a while to ramp up and fight it off, allowing it to do more damage.

Vaccines solve this by exposing your immune system to something that looks like COVID so it can ramp up faster if/when you're exposed to real COVID.

One of the things the immune system does is cause symptoms (fever, coughing, running nose, etc.).

My question is, is this "slow immune system ramp-up" the reason for so much asymptomatic spread (since you become contagious before your immune system catches up), and post-vaccination does your immune system ramp up fast enough that you have symptoms earlier (before or while contagious)?

I've had a lot of trouble searching for this since so many people are surprised that vaccinated people aren't 100% immune and it's hard to find anyone who can be bothered to collect data (and of course, running actual experiments is crazy talk).