I guess I then have to ask are you trying to achieve zero cases or zero deaths. But beware you are opening a Pandora's box by looking to reach zero in either case. Because what happens when Covid-19 has gone to zero but the annual influenza kills even just 1 person the following year. Will we go to masks, lockdowns, distancing for every contagion? At what point will you reach a diminishing return as fewer humans interact with each other and then you find more getting ill and dying from things like the common cold?
Be aware, when I say "you" I'm speaking in general, not speaking of you specifically. This is not a personal question, just hypothetical.
As I said... the "low enough" number is probably something higher than 0. But we don't know what that number is yet. So if you insist on knowing the outside most extreme number -- it's 0. 0 cases per day.
But you also are not understanding what zero means: There are many days in any given town where there are 0 cases of flu. Thus, when cases do pop up, they are manageable. Not to mention, flu is significantly less dangerous Covid.
The more accurate comparison is measles or mumps. On any given day, most communities are at 0 cases of measles and mumps. When there is an outbreak, there is a response.
We don't shut down the entire country for 6 months when there is 1 case of measles. But when there is 1 case of measles, there is vigorous contract tracing. Sources of the outbreak may be shut down temporarily (close the school, for example).
So yes.. the goal is to get down to zero cases in most communities. And then deal with outbreaks as they occur.
Now, as I said above -- we will likely normalize before we hit zero in most communities -- but when we are "low enough" that it appears the numbers will head down to zero, even without masks.
We don't know what that number will be. Maybe it's a level of 4-5 daily cases per 100,000 people, maybe it's 1-2 cases per 100,000 people, maybe it's 1-2 cases per 1 million people.
Australia is a good example -- pretty open and normal right now, but they lock down the locality whenever there is a surge. Currently, their rolling average of cases is 0.25 cases per million people, per day.