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I want to make sure we& #39;re all on the same page when we& #39;re talking about achieving herd immunity through natural infection. Important notes in 
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Fine Print: The model underlying this chart makes assumptions which parallel those made by proponents of herd immunity as a public health intervention to stop the spread of COVID-19. Several of these assumptions are 100% absurd, but here& #39;s what it looks like if we use them.
Specifically, we assume that:
- Once a person has had COVID-19 once, they can never get it again (that& #39;s not true, so in reality the number of cases needed to reach herd immunity is much higher than shown here--in fact we will never reach it through natural infection).
- Once a person has had COVID-19 once, they can never get it again (that& #39;s not true, so in reality the number of cases needed to reach herd immunity is much higher than shown here--in fact we will never reach it through natural infection).
- The “cases needed” estimate assumes that a total of 80% of people under age 65 must become immune through infection and that somehow only a total of 20% of people over age 65 become infected in the process. (This would be practically impossible to achieve.)
80%/20% approximate what is thought to be the herd immunity threshold for COVID-19, or the population level immunity at which the disease would no longer find readily available susceptible people.
- The model assumes that we have confirmed 1 out of every 5 cases of COVID-19 in Wisconsin so far. Or to put that another way, that for every case listed in the WI DHS case count, there are 4 more cases that were never diagnosed.
And in case we want to ignore morbidity entirely, here& #39;s what mortality looks like:
Mortality chart makes two more assumptions, namely that
- Age-specific infection fatality rates will be stable going forward, which implies that
- We won& #39;t run out of hospital beds, ventilators, staff, etc. as this unfolds, so deaths from COVID-19 & other causes won& #39;t spike
- Age-specific infection fatality rates will be stable going forward, which implies that
- We won& #39;t run out of hospital beds, ventilators, staff, etc. as this unfolds, so deaths from COVID-19 & other causes won& #39;t spike
Data sources: CDC’s pandemic scenario planning guidance, Wisconsin Department of Health Services, and Census American Community Survey 1-year population estimates from 2019.
I& #39;m old enough to remember when the GOP was losing its collective mind about death panels.
We& #39;re not even close. Herd immunity through natural infection is unethical & impractical. And even if we were willing to throw ourselves on the pyre, it wouldn& #39;t work in any case. #JohnSnowMemorandum #IllWaitForAVaccineThankYou #HerdImmunityUnacceptable
