Earlier quoted context omitted.
Contract tracing hasn't worked at scale anywhere. It's a nice idea conceptually, but the problem is psychological. People stop caring about tracing when 98% of all trace connections are false positives. If a person is infectious for a week and the r0 is around 1 then only 1 person of all the people they've been in contact with will actually contract the virus on average. The other 50+ people, assuming they can even b…
Contact tracing is working extremely well here in New South Wales. But we have very low incidence of virus in the community, sufficient to get useful early warnings when DNA analysis picks up virus in the sewage system. So once you're down to low levels of incidence in the community, given a robust well organised system, efficient contact tracing does prevent the virus from spreading in the community unchecked.
They have done very good at tracking and locking down the few cases that get out, even with very low mask use in the general community based on what I've seen. People were sensible when it mattered most.