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Thanks.

I assume that you get immune after recovery as most data indicates that this far.

I assume that I can neglect the deaths as these are such a small proportion of the total population, but in a more detailed model this should be included (coming soon hopefully).

Whether different countries have a strategy of herd immunity or not is more of a communication issue than something that actually differs between countries I would say. The strategy that everyone has is to keep the growth so small that their Healthcare system can cope with it while at the same time going fast enough so society does not implode.

As heard immunity is so far away and the path is scary, most countries choose not to comunicate that as a strategy. Instead they focus on the current part of the strategy, namely to minimize the growth rate.

As it is a pandemic, every country would need to reach herd immunity to get things into balance. Some of that immunity could come through vaccines, but it will take quite some time before we have one.

Could not agree more. This leads one to think that we may need to work on general better practices e.g. in medicine considering increasing use of telehealth under even "normal" circumstances (likely to help with minimising all nosocomial infections) and/or that we will have to have repeated periods of increasing social distancing until a vaccine is available.

Current tests are PCR-based, detect current infection (or at least presence of virus RNA, ongoing debate about significance of positivity for infectivity after resolution of symptoms) with SARS-CoV-2 aka virus causing COVID-19, they would not be (true) positive unless someone is actively infected. Tests to detect prior infection with this virus are being developed but not yet available, they are the serologic assays you hear of. Not fully uptodate but good intro here.

I agree with your statements here. Especially with regards to how the communication strategy (especially in the USA) is focused on the short-term mitigation plan, with no articulation of the higher level COVID-19 end-game strategy.

The Chinese model seems impossible for the USA, but the 60% infection for herd immunity is unacceptable. Is seems we are haphazardly stumbling toward a hybrid end game, with a combination of non-trivial number of survivors (~10%?) with immunity, a calibrated relaxing of social distancing (hopefully based on data), desperate short-term increase in hospital capacity, desperate attempts at improving treatment, and slow but massive gearing up test infrastructure.

It seems like what we really need is an R0 model that shows the effect of relaxing social distancing on virus survivors with immunity, relaxing restrictions on some subset of businesses, the effect of certain countermeasures like masks, etc.

Since factors tend to average out over large populations, it should be possible to make a model for R0 based on a few key factors. For example, % of people still coming to work, or % of people still taking public transportation, % of people with access to testing, etc. I suspect that a lot of things people think are important, like wearing masks and wiping down your Amazon deliveries, are basically irrelevant. I would be very interested in research to better model R0 and establish a data-based pareto of factors.