Thread by @professor_dave

Random antibody studies in New York state indicate that statewide, 13.9% of people now have antibodies to the disease. This would mean ca. 2.7M people have been infected. With 21,000 deaths so far this gives a true fatality rate for Covid-19 of 0.78%.
nbcnewyork.com/news/local/2-7…

For context, to achieve 'herd immunity' would require 80% of a population to be infected - so New York State is just one sixth of the way there. New York City, with 21% positive antibody tests, one of the worst affected places in the world, is one quarter of the way there.

This study, showing a fatality rate of 0.78%, allows simple calculation of how many total deaths in a country might be expected before 'herd immunity' would be reached.
USA: 2.56 million
UK: 520,000
Italy: 471,000
Spain: 366,000
Sweden: 80,000

In turn, this also allows rough estimation of how far each country has got, overall, towards herd immunity based on how many deaths have actually been seen across these countries.
USA: 2.0%
UK: 3.7%
Italy: 5.5%
Spain: 6.2%
Sweden: 2.7%

In other words, to raise population level immunity, countries would need to go through what we have already been through about 20 times over. Even New York City, the worst affected place in the world, would need to go through it 3 or 4 more times.

This is not really an option we can contemplate and clearly demonstrates why the development of effective treatments, or even better a vaccine, are the only games in town.

It's worth noting that a fatality rate of 0.78% also has to be treated with some caution. Although New York has counted hospital and nursing home deaths, it has not counted deatgs/impacts in the wider community. So that number may rise.

Also although the number of people with antibodies has been counted, some people infected at the same time are still dying, so again that will cause the fatality rate to rise. As such a 0.78% fatality rate should probably be treated as a lower threshold.

Annoyingly, I messed up the calculation, and will correct it here before a 'herd immunity zealot' shouts at me - I did 0.78% of the full population, not 0.78% of 80% of population. The numbers are 'only'
USA: 2.04 million
UK: 416,000
Italy: 377,000
Spain: 293,000
Sweden: 64,000

Again, just adjusting these for me getting the previous numbers a little wrong (see response to tweet above)
USA: 2.5%
UK: 4.6%
Italy: 6.9%
Spain: 7.8%
Sweden: 3.4%
(the conclusions that follow in the thread still all hold)