You don't need 80% coverage though. Influenza would be a pandemic too (and has been!) but is well controlled by the existing regimes. There's nothing all that notable about covid really, beyond its novelty. Once the bulk of the population has some immunity, even if incomplete and even if it needs a regular refresh, we hit herd immunity: R0 drops below 1 and the disease stops spreading. There's no reason to expect this to work any differently.