I think you've been misinformed here. Their strategy is still herd immunity. Some officials have said that's a bad way to characterize it - that their strategy consists of the things they do to mitigate harm, not the epidemiological fact that will eventually bring the outbreak to an end. (And I think that's fair - nobody calls the strategies that were applied during the Spanish Flu "herd immunity".) But they don't have any plan for ending the outbreak other than lots of people catching it and becoming immune.
It can be physically done yes but it cannot be done because of political and cultural issues.
A critical mass of people will continue thinking it's less serious than the flu (these retracted studies not helping it) until it gets so bad that it becomes impossible (e.g. everyone knows someone they really care about who died). That's when proper lockdowns are politically possible.
It has, but nobody really knows why they've been successful. The people who say it's just testing and contact tracing are misleading. Sweden was testing and contact tracing, like most countries were, but it failed to contain the virus.
And we should be cautious about even the idea that they've been successful; people used to believe Japan and Signapore had contained it too.
It's not much of a mystery. The lockdown was much more complete, and was accompanied by additional measures to separate and quarantine sick people. There message wasn't, "Stay home if you're sick (and infect your families, and maybe your neighbors too)." Sick people quarantined apart from their families. People went door to door to measure temperatures. Food was delivered to neighborhoods, so that people didn't have to go out at all. That's how they brought the number of active cases to a low, manageable number.
Now, they have extensive testing, and they use cell phone data to assist contact tracing.
Basically, what's needed is a capacity for organization and discipline that seems lacking in many countries that are struggling.
It doesn't have to. Suppress transmission with lockdowns and quarantines until the number of cases is low. Then open up partially, with social distancing measures, mask requirements, etc. Do contact tracing with extensive testing and contact tracing to keep the virus at a low level. Use random testing to keep an eye on the level of the virus in each community. Impose stricter measures locally if you detect R > 1.
In China, it was suppressed to somewhere around 0.3. They went from nearly 4000 new confirmed cases per day in early February to about 100 new confirmed cases per day (at a much higher rate of testing) a month later. New cases are low enough now that contact tracing appears to be holding the epidemic in check.
Once you reach a low overall case count, you can ease measures to target R ~ 1.
The alternative, letting the epidemic burn through the population, means sacrificing ~0.5% of the population.
Given the steady pace of ~30k new confirmed cases per day in the US, R has not been suppressed enough. Yet governors are talking about easing restrictions...
