There's a big difference between zero cases and one. When there are zero cases, you can (assuming a tight border and quarantine) act more-or-less as you did pre

There's a big difference between zero cases and one. When there are zero cases, you can (assuming a tight border and quarantine) act more-or-less as you did pre-pandemic. This is what most of Australia has been like, and what Sydney was like before this lockdown. When you have a small number of cases, you still have to take precautions to keep the reproduction rate below 1.0. It's up to each society to decide which strategy it wants to take. Australia has chosen eradication (zero cases) over suppression (a low and flat number of cases). The former lets you have periods of pre-pandemic behavior punctuated by short but extreme lockdowns, the latter means you get a constant set of restrictions until enough people are vaccinated.