What About Herd Immunity?

What is herd immunity and what does it mean for us?

Dick Dowdell
2 min readDec 17, 2020

You probably already know this, but I keep hearing that herd immunity will end the COVID-19 pandemic. That is true, but herd immunity is not free. We have to pay for it by getting vaccinated or with lost human lives. I’m not spouting propaganda. In my younger days, I studied Biology at Brown and was trained as a Biological Warfare officer (defense, not offense) in the Army. I know the meaning of the terminology and I know how to run the numbers.

Herd immunity, more properly called group immunity, is a form of indirect protection from infectious disease that occurs when a sufficient percentage of a population has become immune to an infection — either through vaccination or previous infections — thereby reducing the available vectors for a disease and thus the likelihood of infection for individuals who lack immunity.

The current U.S. population is approximately 331,000,000 people.

To achieve group immunity, between 83% to 94% (possibly as low as 75%) of the population must have acquired immunity to COVID-19, either through vaccination or previous infection. Which means 274,730,000 to 311,140,000 individuals need to have acquired immunity to achieve group immunity.

The current mortality rate from COVID-19 across all recorded infections is 1.8% which means that 1.8 out of every 100 infected people die from COVID-19. That, in turn, means that reaching group immunity without vaccination could cost 4,945,000 to 5,600,000 American lives. That is utterly horrifying to me.

Statistically, with modern vaccine technology, SAEs (severe adverse events) are exceedingly rare — far, far lower than the COVID-19 mortality rate. Despite the math, fewer than 60% of Americans say that they will get vaccinated — far short of the 83% to 94% needed to achieve group immunity and quell the pandemic. The price of misinformation and disinformation with its resulting ignorance may be millions of American lives.

Be smart and be safe.

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Dick Dowdell

A former US Army officer with a wonderful wife and family, I’m a software architect and engineer who has been building software systems for 50 years.