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):

% (US reference: ~30-40%)

Total population vaccination rate (with 1+ dose):

% (US reference: ~55%)

Vaccination rate among previously infected individuals

(should be slightly lower than the total vaccination rate):

%

(US reference: ~45%)

Total Population Immunity:

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

These are best estimates based on the latest research, taking into account the variants.

Average vaccine efficacy:

Average natural immunity efficacy:

Average vaccine + natural immunity efficacy: