I don't like the term herd immunity

(Image credit: Sven van Echelpoel/Flickr)

"Herd immunity" keeps popping up as a public health policy even though most epidemiologists dismiss it as an unwise prescription. I previously wrote about herd immunity in a post titled "The shift to antibody testing is a choice of death over life" which highlights the high cost in human lives of such a policy pursued through community spread.

Let's review a few other implications of a "herd immunity" policy. There are two proposed paths to reaching herd immunity: through vaccination or through community spread.

Fairness

Herd immunity through natural infections is inherently unfair. The consequent deaths are unevenly distributed across the population. I'm not just talking about the underlying characteristics of the illness, which attacks certain demographics, such as the elderly, while apparently sparing other subgroups, such as the very young.

I'm referring to the differential access and quality of healthcare - which is a major contributor to differential mortality in minorities and lower-income communities. Moreover, I'm pointing to the heightened exposure to the virus due to economic conditions and the nature of one's work. Essential workers, workers who must serve others in person, and people who cannot afford temporary unemployment bear the burden of a "herd immunity" policy. There hasn't been much discussion about how these subgroups should be compensated for the "sacrifice" society demands of them, if the government chooses such a policy.

Fatalities

The only proven way to achieve herd immunity is by broad-based vaccination. This is also the safe path since a 50% effective vaccine cuts the death rate by half relative to achieving herd immunity through community spread. (It is also not clear how much immunity one gets from an infection.)

Attempting to reach "herd immunity" via natural infection not only doubles the number of fatalities (relative to vaccination) but also inflicts disproportionate harm on disadvantaged subgroups.

Rewarding the wrong behavior

Herd immunity via vaccination is widely held as desirable, even though we are praising the wrong entity. What we desire are the vaccines that protect us from the virus. Herd immunity is actually not an indicator of success but of failure. Let me explain.

If we have an effective and safe vaccine, everyone should take it. In practice, when 75 percent of the population have been vaccinated, we have defeated the virus, in the sense that the community spread will have been curtailed, whether or not the remaining 25 percent get the vaccine. (The proportion that needs to get vaccinated depends on how fast infections are occurring; I'm using 75 percent for illustration.) It's the 25 percent who benefit from "herd immunity" while the other 75 percent are protected by the vaccine. The 25 percent are the bystanders who get windfall from the actions of the other 75 percent.

A society does not have to, and probably should not, stop at 75 percent. If everyone gets vaccinated, we have comprehensive immunity, rendering herd immunity immaterial. That's what I mean when I say herd immunity is a sign of failure.

Herd immunity rewards non-cooperative behavior.

Tying your health to others' actions

If you are considering being a bystander, think twice. The more people who intend to sit out, the higher the chance that the society will not reach the 75 percent threshold to get herd immunity. In that world, the death rate of unvaccinated bystanders will be double that of the vaccinated (or worse, if the vaccine is better than 50% effective).

By sitting out, you have tied your own health to the actions of other people. Worse, you have tied your health to the actions of people who hold opposite views as you.

Immunity in theory

If you are still considering holding out, think again. Perhaps no one has told you that herd immunity is an abstract mathematical construct. The bystanders do not have immunity in the biological sense of the word.

If they come in contact with the virus, they may get sick, and even die from Covid-19. The mathematical theory predicts that once 75 percent of the population is vaccinated, the odds of an unvaccinated person contacting an infectious person is small enough that the epidemic will not grow further. Such implied mathematical immunity is different from getting immunity from a vaccine that stimulates our bodies to manufacture antibodies that fight the coronavirus.

The unfortunate wording of "herd immunity" fosters the misunderstanding that it gives individuals "immunity" from getting sick.

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tl;dr

Herd immunity draws attention to non-cooperative behavior away from the scientific achievements of vaccines. The people who stand to benefit from herd immunity don't even have immunity, as they will get sick if they come in contact with the virus. That's why I don't like the term herd immunity.

Comments

[Michael Droy]

You are somehow presuming that Covid is a major threat relative to other health (and economic) threats.
Avoidance of a herd immunity policy means more cancer deaths, more anything else deaths, horrendous psychological problems for adults, worse for children, and so on and so on.

"Which saves more lives: herd immunity or vaccinations?" is a mute question.
The real question is does lock down kill more than Covid either way. Yes it does.

[Kaiser]

MD: I'd be interested in reading studies that quantify those other effects with data. So far, we know we have suffered significantly more excess deaths, which no one has explained other than Covid19. Vaccination is the primary path to achieve herd immunity so those two are not opposing concepts.

[Michael N]

Herd immunity is necessary! Some people cannot receive vaccines, others have immune system issues that prevent vaccines from working. Yes, these people will always be vulnerable. By reaching enough community immunity that a threat is entirely eliminated, this population is protected. That is the real need for herd immunity. The conclusion is the same: if you are able, you should be vaccinated. But the reason is to protect the people who cannot be protected.

[Kaiser]

MN: That is a valid point. Some of the 25% will be people who, say, have specific adverse reactions to the vaccine. However, they should be an absolute minority of the estimated 80 million people! Further, they should be informed of the points in my post: that they can get sick if they get in contact with the virus, and that they should encourage their friends and neighbors to get vaccinated.

[Michael Droy]

Kaiser: you only have to at cancer diagnosis. There is plenty of doctors out there willing to testify that diagnosis of cancer in UK has fallen by half to three quarters.
Either Covid or Lockdown has prevented a great deal of cancer very quickly, or that is a lot of cancer patients who will get diagnosed very late. Cancer doctors do predict that that will mean more excess deaths from cancer than Covid. And of course it will be taking 10s of years off their lives instead of 1 or 2.

I'm another case. With access to a doctor or specialist heart consultant I would have had the need for an angiogram diagnosed and the 3 stents I needed.
I had to get into hospital another way - collapsing while running with a heart attack right in front of the A&E registrar who was cycling on his way to his evening shift. Even he couldn't save me without the fortunate arrival of a police car with a defibrillator. I thanked him 40 mins later when my ambulance delivered me to his A&E department.

The bottom line is that Covid is reducing the life expectancy of humans by about 2 months. In UK life expectancy rose by 6 years to 81 over 1987-2017. We got those extra 6 years of life because of the growing economy, better lifestyles, and much improved health services. Killing the Golden Goose of Economics and health services rather than accept a 2 month set back is lunacy

Like Covid itself, the over-reaction of the immune system by governments, media and "those that feel obliged to react" is killing the patient.

[Ken]

Michael Droy: Lack of medical care is more likely due to doctors making themselves unavailable or being diverted to care for the large-number of covid-19 patients. 60+ year old doctors do not want to see lots of patients for procedures. Hospital administrators don't want them to, anyway, because their budgets are stuffed. They didn't lockdown hospitals they repurposed them as covid-19 treatment centres.

I won't comment on how to describe someone who had symptoms that required an angiogram and then went running. One thing that all lockdowns have is to allow access to doctors, so why didn't you.

Your death figures look like they are made up.