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COVID-19 Population Immunity Calculator
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COVID-19 Population Immunity Calculator

This calculator attempts to estimate the true proportion of a population that have immunity against COVID-19. Given just the natural infection rate and vaccination rate, one can estimate the total population immunity against COVID-19 in any region.

Traditional immunity estimates only look at a single metric: vaccination rate. But there are two main issues with this:
Not all vaccinated individuals are protected (since vaccine efficacy is not 100%)
They do not take into account acquired immunity from those who have previously been infected with COVID-19. This calculator attempts to correct for these two major issues to give a more accurate representation of the total population immunity.
for the spreadsheet behind the calculators (including raw formulas).

Inputs

Natural infection rate (% already infected):
000
25
% (US reference: ~30-40%)
Total population vaccination rate (with 1+ dose):
000
65
% (US reference: ~55%)
Vaccination rate among previously infected individuals
(should be slightly lower than the total vaccination rate):
000
55
%
(US reference: ~45%)

Total Population Immunity:
66%

Note: Even if population immunity is at or near herd immunity, local outbreaks are still possible (and even likely given new variants). Even if protection is not 100%, vaccines are near 100% effective at protecting against hospitalizations & deaths.

Efficacy Constants

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