Measles is a good comparison IMO. It's an extremely contagious virus (even more so than Omicron covid) and can have some serious illness in a small percentage of people. Very similar to covid statistically.

Yet we don't lock down at the first sign of a measles outbreak. Where I'm from almost everyone got vaccinated and a lot of kids had it anyway. The one big difference is that an infection seems to convey pretty much lifelong protection.

Smallpox is a different thing, very serious but not so contagious so it was easy to stamp out.