I do not believe in herd immunity as a strategy in this case. The danish doctors that are proposing it are in disagreement with WHO, and with leading epidemic fighters, and demonstrate lack of understanding of the math behind. They are thinking Flu, and are very bad at taking in learnings from recent epidemic cases like bird and swine flu. Luckily for us our “CDC” are not as conservative as the sweedes, that is a tragedy unfolding before our eyes. R0 is too high. With an R0 of 2.6 (in Freedom units, 2,6 in Denmark ), you will need an incredibly high immunization percentage. 50% immunization would not be enough, it would (if standing alone) bring R0 down with half, to 1.3, which is still way above 1. 75% is a more likely number. It would cost between 0.75% to 3% of the population. The hospitalization rate seem to be quite high, so if the mortality rate has to be in the low end, in order to not overwhelm the hospitals, the time it would take in a highly speculative “controlled” scenario to get enough infected would be much longer than it will take for the vaccine to arrive. It is never going to happen as a strategy. No government of ours will take such a road, and you have to be very detached from the political reality as a doctor to propose herd immunity as an active strategy. It took quite some arguing at home to convince my wife. She is a medical doctor, phd, and she is really good at her job. However, she has not been working with these epidemics beefore, and that is core to the issue. Herd immunity might happen by accident, or rather, by catastrophe. Maybe Italy, Spain, UK, and Sweeden will get to Herd immunity. Or maybe they will just loose 10-20% of their elder population, the virus mutates (because so many are infected), or the immunity wears off, and they end up the same place where they started. We will get vaccines before herd immunity. We must... (The situation in Sweeden is that they have not locked down, and are accellerating into the epidemic, many daily deaths and they now have Covid 19 on a large number of their elder care facilities).