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On the Origins of Herd Immunity

When did we start talking about herd immunity?

“Though coined almost a century ago[8], the term “herd immunity” was not widely used until recent decades, its use stimulated by the increasing use of vaccines, discussions of disease eradication, and analyses of the costs and benefits of vaccination programs.”

Fine et al on “Herd Immunity”: A Rough Guide

Paul Fine’s “almost a century ago reference” was by William Whiteman Carlton Topley and Sir Graham Selby Wilson, The Spread of Bacterial Infection. The Problem of Herd-Immunity, published in 1923.

It has long been thought that Topley and Wilson first used the term herd immunity back in 1923.

An article in Lancet, Some Fundamental Factors Concerned in the Spread of Infectious Disease, published in 1924 does give Topley and Wilson credit for coming up with the term.

On the Origins of Herd Immunity

That wasn’t when the term herd immunity was first used though.

There are earlier references.

There is a reference to herd immunity in the Oregon Agricultural College Experiment Station Director’s Report 1918-1920.

An article about natural herd immunity was published in 1921.
They are talking about brucellosis, which is now a vaccine-preventable disease in cattle.

The report, published in 1921, was talking about natural herd immunity.

In an even earlier report of the New York State Veterinary College at Cornell University for the year 1916 to 1917, R.R. Birch used the term when talking about vaccinating pigs against cholera.

This report about herd immunity and vaccines was published in 1918.

His report, Garbage Feeding, and the Care of Garbage Fed Swine, was published in 1918.

“If properly carried out, a large proportion of each infected herd should be saved and become exceptionally valuable on account of the immunity which would be established.”

Melvin et al on The Control of Hog Cholera, With a Discussion of the Results of Field Experiments

A 1917 book, Contagious Abortion of Cattle, also talked about natural herd immunity.

“Thus a herd immunity seems to have developed as the result both of keeping the aborting cows and raising the calves. Therefore it seems safest for a herd owner to raise his own calves and avoid bringing in new infection.”

Adolph Eichhorn and George M. Potter on the Contagious Abortion of Cattle

Are there any earlier uses of the term herd immunity?

Just a year earlier, Adolph Eichhorn and George M. Potter used the term during a presentation at a meeting of the American Veterinary Medical Association in Detroit, Michigan.

“A definite herd immunity seems to have been established. This has an important bearing upon control measures, and is the principle underlying one of our recommendations which will be referred to later. Moreover, the work of the English commission has shown that a serviceable degree of immunity can be induced by the injection of living organisms several weeks before breeding.”

Eichhorn and Potter on The Present Status of the Abortion Question

Still, it is said that Wilson originally got the idea for herd immunity from Major Greenwood, the foremost medical statistician in the UK.

Is this the English Commission that Eichhorn and Potter were talking about?

“Wilson later recalled that he had first heard the phrase “herd immunity” in the course of a conversation with Major Greenwood…”

Paul Fine on Herd Immunity: History, Theory, Practice

When would they have had that conversation?

They were both Fellows of the Royal Society and after World War I, were working quite near each other in London. Major Greenwood was at the Lister Institute and Wilson at Charing Cross Hospital medical school.

It is also possible that Greenwood, Wilson, and Topley could have talked during WWI. Greenwood and Wilson served in the Royal Army Medical Corps and Topley in the British Sanitary Commission. Before the war, both Greenwood and Topley had started working in London around 1910, and may have talked about herd immunity then.

Whoever first coined the term, it is clear that many of the first reports about herd immunity were about vaccine induced herd immunity. And that those that discussed natural herd immunity stressed that it could only work in a closed system.

Unfortunately, we don’t live in a closed system, which is why natural immunity doesn’t really work. As new babies are born without immunity and their maternal immunity wears off and people visit from outside the community who may reintroduce disease, you will get outbreaks. At least you will unless everyone is vaccinated and protected and until you eradicate the disease.

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