• 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.

  • $\begingroup$ You need to infect 60-80% of the population. So: Far, far (any many deaths) away. $\endgroup$
    – Chris
    Jul 19, 2020 at 15:58
  • 2
    $\begingroup$ I’m voting to close this question because it is not about biology in the terms of SE Biology but a request for statistical information about the medical state of the population in a particular country which will be out of date next week. $\endgroup$
    – David
    Jul 19, 2020 at 16:41
  • 1
    $\begingroup$ You are very welcome to SE Biology, but please read the tour where you will find what sort of questions are suitable here. There is a list of sources of information about coronavirus in answer to one of our Meta questions, or your question may be more acceptable on SE Medical Sciences. $\endgroup$
    – David
    Jul 19, 2020 at 16:47
  • $\begingroup$ @David I understand your criticism, but you are applying it very inconsistently, as many other answers are tied to particular "current" timeframes and events. biology.stackexchange.com/questions/94024 biology.stackexchange.com/questions/90793 $\endgroup$ Jul 19, 2020 at 20:01
  • 1
    $\begingroup$ I am not applying it inconsistently, thank you. I voted to close each of those questions and downvoted them. I was responsible for the Meta post (later adopted as a Community post) aimed at deflecting such posts in a more appropriate direction. The fact that sufficient others did not support me makes no difference to whether or not my view is correct. My reading of the Tour and Help for this site gives me no reason to believe it is not. $\endgroup$
    – David
    Jul 19, 2020 at 21:45

1 Answer 1


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.

  • $\begingroup$ I am curious why you are using the SE Q&A format to post your calculations on SE Biology. Would I be allowed to tell Stack Overflow about the current stock market price of computer chip companies or the percentage of European networks that depend on Huwai? $\endgroup$
    – David
    Jul 19, 2020 at 16:52
  • $\begingroup$ Paul, perhaps you should generalize your question, e.g. to be about how one can find out how close a country is to reaching herd immunity. Then your answer can be modified a bit to explain how to calculate and use current U.S. numbers (showing how they were found) as an example. $\endgroup$
    – mgkrebbs
    Jul 19, 2020 at 19:50
  • $\begingroup$ @mgkrebbs I feared that would be too broad. FWIW, StackOverflow would be an odd choice for your computing cost question, as SO is focused on software, but people can and do ask such questions on ServerFault. $\endgroup$ Jul 19, 2020 at 23:29

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