D-I-Y HERD IMMUNITY CALCULATOR
Yesterday I posted an essay explaining herd immunity. I used some accepted numbers to make the calculations.
You may have questions about those assumed numbers. So, today I would like to give you two tools; the first will allow you, yourself to estimate how many people need to achieve immunity to stem viral spread, and the second will allow you to estimate the total number of deaths in this country that would occur based on your own assumptions.
A short introduction to the tools.
R-Naught expresses the amount of people that a single individual is likely to infect.
The % of people needed to become immune in order to stop viral spread is expressed as 1-(1/R0).
Lethality is the percentage of people who would be expected to die compared to those infected.
THE FIRST TOOL: HOW MANY PEOPLE NEED TO BE IMMUNE?
The first tool is the chart shown here. This chart plots R0 versus the % of people needed to achieve immunity.
I used two numbers in my essay. I used an accepted R0 of 5.7 if no protective measures were taken, and 1.4 if those measures are taken. You may choose your own value for R0 and look at the percentage of people that will need to be immune. The most common % of the population needing to become immune cited in the media is between 60% and 70%. I have highlighted that range in the chart.
If you choose this range, then the R0 expected would be between 2.6 and 3.4. Note that because this is NOT a linear function, even if you choose an R0 of 2.0, you would still need to reach 50% herd immunity to stem viral infection.
THE SECOND TOOL: HOW MANY PEOPLE WILL DIE?
The second tool is a table that will allow you determine how many people can be expected to die based on your choice of R0. The table lists all of the R0’s and then charts the deaths expected based on lethality. In my essay I used a lethality rate of 2.2%. Again, you may choose your own value for lethality. I have highlighted the range of lethality that would result in a need for 60% - 70% herd immunity as determined from the previous tool.
Observation of protective actions and respect for protecting your fellow citizens will temper the effects on the entire population.