Friday, June 19, 2020


It’s been a few weeks since I’ve posted about our old nemesis COVID-19 but sticking my fingers in my ears and singing la-la-la has not made it go away. So, I’m back to address one of the more persistent pseudo-scientific rumors about the disease that is floating around: that if we just let things take their course, “herd immunity” will eventually be built up in the population to protect us.

What is herd immunity? An article by the Johns Hopkins Bloomberg School of Public Health defines it this way: “When most of a population is immune to an infectious disease, this provides indirect protection—or herd immunity (also called herd protection)—to those who are not immune to the disease.” Herd immunity, or protection, is thought to be reached when a population is 70-90 percent immune to a disease.
Protected--with a little help from my friends.
This was the reasoning that led Sweden to choose a path different from its other Scandinavian neighbors (and, indeed, all of Europe) in its response to the coronavirus pandemic. There was no government-mandated lockdown in Sweden; schools, businesses, even bars and restaurants remained open (and still do). The only restriction was on gatherings of over 50 people and recommendations that people with symptoms self-quarantine and the elderly limit their movements outside their homes. 

The result was one of the highest per capita fatality rates in the world, ten percent of cases, according to data from Johns Hopkins University. Public health officials in that country may be reconsidering their thinking but have made no changes yet. They are blaming a rise in cases on increased testing, much as our own government is.

Still, Sweden’s top epidemiologist, Anders Tegnell said, "If we were to run into the same disease, knowing exactly what we know about it today, I think we would end up doing something in between what Sweden did and what the rest of the world has done," according to a Reuters translation.

The problem with this reasoning, of course, is that almost no one in the world was immune to COVID-19 when this pandemic began. It was a new disease, unknown to human immune systems and free to wreak havoc on our bodies. To go from near zero percent immunity (in a disease with a ten percent fatality rate) to 70-90 percent immunity without vaccination or massive death is impossible. Of course, we don’t have a vaccine for COVID-19. Therefore, herd immunity to this disease is not an option.

If you are old enough to remember the days before there was a vaccine for the childhood disease of chicken pox, your mom may have “inoculated” you against the disease by sending you over to visit a neighbor child with the disease so you caught it young. Having chicken pox as a teenager is far more miserable than when you’re six. (Trust me. Both my best friend and my husband can testify to this. I was lucky enough to endure the rash and fever as a youngster.) 

But moms could afford to do that with a minor illness like chicken pox (nobody knew we’d end up with shingles decades later). COVID-19 can kill you. There’s no deliberately infecting yourself with this disease in the hopes of having a mild case and thereby increasing “herd immunity.” Until we have a vaccine, there will be no herd immunity to COVID-19.

There has never been herd immunity without vaccination. There were at least three worldwide pandemics of plague in ancient times, though each killed roughly a third of the population before it burned out. Smallpox was a worldwide scourge before it was eliminated by a concerted effort to vaccinate everyone, everywhere. Polio killed and maimed millions before Drs. Sabine and Salk developed their vaccines, and still remains a threat in Third World countries (which is why we still vaccinate our children as a precaution against possible infection from abroad despite elimination of the disease in the U.S.). Measles, mumps and rubella (MMR) and diphtheria make a determined comeback anytime and anyplace vaccination efforts lag, such as in communities where anti-vaxxers are active or in poor or Third World communities now that the pandemic is limiting access to health care. 

"Natural” herd immunity doesn't exist. That is a myth. Herd immunity comes through vaccination, by which those who cannot be vaccinated, for health reasons, benefit from the vaccination of all the others around them. When we have an effective vaccine for COVID-19, and we can distribute that vaccine to everyone, everywhere, then we can hope to achieve herd immunity for this disease. Not before.

Cheers, Donna

Information for this post provided by:
“What is Herd Immunity and How Can We Achieve It With COVID-19?,” by Gypsyamber D’Souza and David Dowdy, COVID-19/School of Public Health Expert Insights, April 10, 2020.
“In Sweden, Where No Lockdown Was Ever Implemented, Coronavirus Cases Reach Record High,” by Meghan Roos, Newsweek, June 12, 2020.


  1. As a scientist, this has depressed me perhaps more than anything, that no matter how much scientific evidence is presented, the powers that be choose to ignore it. My government is busy pretending that herd immunity wasn't the play all along after seeing the initial announcement go down like a lead balloon, and are now doing it by stealth. It was bad enough thinking they were deliberately trying to kill us off. It's the added fact they don't even care.

  2. I'm with you, Pippa. The denial of science drives me bonkers on so many levels--from this flawed theory to the refusal to wear masks. We have new evidence since I wrote the post that herd immunity is not working anywhere--testing is showing antibodies in as little as 17 percent of the population even in places with high infection rates like Italy, Spain and New York City. That's a long, long way from 70-90 percent "herd immunity." Because SCIENCE.

  3. And then they say scientists are such doomsayers...


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