@McWobble I think the other consideration is whether other steps that will be taken will reduce the R0 sufficiently to make a dent in the numbers. Closing bars and restaurants for example, more social distancing.
What I don't understand is what is Spain and Italy's strategy? Are they hoping a lockdown stops transmission so most of the population never catch the virus or do they expect many millions to catch it and the lockdowns are a tool to flatten the curve and reduce the R0
Like you I would be concerned with a strategy to stop it in its tracks like China. We are at least 12 months from a vaccine. Can countries with high freedom of movement maintain a lockdown or semi lockdown for a year?
I am sure McWobble will come along and give us great answers to your question, but I think the 1) "herd immunity" scenario, which would only have any meaning if 60%+ caught it etc. etc., and 2) flattening curve so demands matching nhs surge capacity scenario, are mutually exclusive. Scenario 1) will likely throw tens if not hundreds of times of patients nhs can handle into their ICUs as I alluded to above. Think this is why many including me are so unhappy with Boris/CMO/CSA's "plan", which hitherto has not done enough to flatten the curve.
I think it is kind of funny that on one hand i) we say people here will not adhere to distancing restrictions like that in Korea, and it is a reason why we should accept 60%+ catching it in a wave so that we can be immune happily after, while on the other hand ii) the latter requires putting the elderly and ill young in much much stricter isolation for months, because with i) the vast majority of the population remains uninfected hence inevitable carelessness are unlikely to infect - only 0.17% of Hubei are infected e.g., while for ii) the vulnerable will be living amongst everybody who are either infected or to be infected and none of them would know who's still infectious but they are all around them. If i) won't work here, why would ii)?
On top of that, do we accept that: a) nobody knows if herd immunity works for this new virus, b) hitherto for killer virus countries developed and relied on herd immunity by giving the vast majority vaccines, not a virus that kills, c) for the under 70 who did not get infected in the wave do we make sure they get infected to make up the 60%+ infected necessary, knowing it kills the young too and about 3.6% of 60-70 - do we not call that murder?, and d) even if ALL the young(er) got infected and were indeed immune next season/years, does it really put the country in a safe harbour, when someone in the Women's Institute caught it from her visitor from Timbuktu?
Why Italy and Spain, and indeed France are locking down? I think it is because nobody will risk killing close to a million to test a hypothesis with implementation challenges, will you? The only thing that is proven to "work" (only for now I admit, and it does take at least a couple of weeks to flatten the curve), is what they did in China, Singapore, Hongkong, Korea. Nobody said they are home and dry, and who knows what happens when they reopen their schools? But at least they bought themselves time and a chance, without having to kill millions.
And they are learning - I believe in Hongkong nowadays literally everyone of the few they might identify each day are associated with travellers entering the territory. So if tests can be developed with quicker result turnaround (4 hours is quickest atm I think), that door can potentially be shut with limited downside and cost too, without vaccines.
Some defend the government accepting a wave of infection to develop herd immunity by saying it may be less adverse economically and socially compared to a lockdown strategy. Has anybody seen any comparison? How many have they assumed would die from tens of millions being infected, and what are the economical and social consequences of that?