How close is the U.S. to herd immunity, assuming long-term immunity?

Question

Assuming:

infection always results in death or immunity (unproven, but no evidence of repeat infections yet)
official COVID-19-related death counts are accurate (142k at the time of this question)

How close is the U.S. to achieving herd immunity to COVID-19?
The CDC has published estimates of infection rate, mortality rate, etc. However, I haven't yet seen anyone actually do the math of how close the U.S. is to herd immunity.

Paul Draper · Answer

The CDC estimates R0 to be 2.5, meaning that (2.5-1)/2.5=60% of the population must be immune to achieve herd immunity.
(That is, under 60% immune and the # of cases will increase; over 60% immune and the # of cases will decrease.)
The estimated IMF (infection mortality rate) is 0.65%.
So 60%*0.065%=0.39% of a population will die to reach herd immunity.
To date, 142k people in the U.S. have died from COVID-19, out of a population of 328M. So 142k/328M=0.043% of the population has died.
Thus, based on reported deaths, the U.S. has 11% of the required infections/immunity to produce herd immunity.

Note that this assumes that high- and low-risk individuals are exposed at the same rate. If more of these infections happen among low-risk individuals, the effective IMF is lower, yielding fewer deaths to produce herd immunity. And the inverse is also true.

How close is the U.S. to herd immunity, assuming long-term immunity?

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