In regard to South Korea, I posted a graph a week or so ago which compared the number of tests being carried out there with the number here in the UK. They are testing a fraction of the number of people we are which may explain why they aren’t seeing as many infections (the same applies to Japan incidentally).
I think South Korea and Japan are more comparable to Australia in that they effectively closed their borders on 1 April and have not re-opened them since (they either disallow entry from foreigners or mandate a two weeks hotel quarantine).
Track and trace systems seem to work quite happily with closed borders and very low case numbers, but don’t work when you get a decent number of infected people in the population - e.g cities in Germany such as Berlin and Frankfurt have now given up on their supposed gold standard track and trace and are just asking people to do it themselves now. I am of the opinion that a ‘gold standard track and trace system’ people are calling for during the ‘circuit breaker’ is another red herring like the moonshot testing etc.
For relevance to our lockdown, I doubt going into winter we will see sufficient decreases in cases in a month to give a track and trace system a chance. That just means extending it further into winter, based on what would just be a hypothesis
