Friday, April 10, 2020

The Herd Immunity Strategy Is Better--for Life and Liberty--Than Trump's Lockdown

"The Herd.  They call it the Herd."

In his press conference Tuesday, President Trump said that in dismissing Sweden's "herd immunity" strategy for handling COVID-19 as inferior to his strategy for fighting the pandemic through an economic and social lockdown of the country.  He said that his strategy will save hundreds of thousands of lives that would be lost without a national lockdown.

In response to Trump, Swedish Foreign Minister Ann Linde said that it was "factually wrong" for Trump to say that Sweden was pursuing a herd immunity strategy that would allow many people to die from COVID-19.  On the contrary, she said, Sweden has taken many precautions to minimize the deaths from the disease.  Sweden's chief epidemiologist, Anders Tegnell, has said, however, that their strategy is to have a gradual spread of infection to slowly build up herd immunity.

Sweden has not closed its primary schools, although it has closed its secondary schools and higher education.  It has advised its people on how to reduce the spread of the disease through social distancing.  There has been no legally enforceable "stay at home" order, although those over the age of 70 have been advised to stay home.  It has relied mostly on voluntary compliance.  And it has not shut down large sectors of its economy as has been done in the U.S., the U.K., and elsewhere.

As of this morning (April 9), the count of deaths from COVID-19 in the U.S. is 14,802 (in a population of 322 million), and in Sweden it is 8,647 (in a population of 10 million).  The rate of deaths per million is higher in Sweden (68.02) than in the U.S. (44.76).  Some of the critics of Sweden's strategy see this growing death rate as a sign of failure.

As I have argued in my previous post, developing herd immunity is the natural human defense against contagious diseases rooted in our evolved human immune system; and it does not require the sacrifice of life and liberty through an economic shutdown.

Two of the clearest statements of the herd immunity strategy come from David Katz and from Dr. Knut Wittkowski.  On the other side of this debate, Gideon Meyerowitz-Katz summarizes the arguments against this strategy.

Herd immunity is the idea that when a sufficiently large proportion of a population of people become immune to a contagious disease--either through previous infection or vaccination--the spread of the disease gradually slows, and eventually it disappears, because the chains of person-to-person transmission have been broken (Fine, Eames, and Heymann 2011).  The critical point at which a population has become immune is called the "herd immunity threshold" (HIT), which is calculated by estimating the "basic reproduction number"--the average number of new infections caused by each infected individual--and multiplying it by the proportion of the people in a population who are susceptible to infection.  So the higher the contagiousness of a disease the higher its HIT.  The estimated HIT for the COVID-19 disease is 70% to 80%, so that the disease will slow down or even disappear once 70% to 80% of the individuals in a population have been infected and thus have acquired immunity.

Herd immunity has evolved by natural selection as the natural defense of human life against the aggressive attack of disease-causing microorganisms that move through human groups by person-to-person transmission.  At the same time, however, these pathogenic microorganisms have evolved by natural selection to develop countermeasures to overcome our natural defenses.  Viruses mutate, and in rare cases, those mutations create new kinds of viruses that can pass easily through human populations in which most people do not yet have immunity to the virus.  The COVID-19 virus has done this.

Achieving herd immunity for this new virus will require that many if not most of us become infected.  Most of the infected people will feel no symptoms or only mild symptoms.  A few of us will become sick enough to require hospitalization.  And of those who become severely sick, a few will die.  Most of those who die will be older people who were already vulnerable become of previous health problems.

Now here comes the debate.  Over the past month, many political leaders have taken the advice of some epidemiologists that we have a moral obligation to reduce the deaths from the COVID-19 virus by shutting down large sectors of our societies to slow down the spread of the virus until we have a vaccine that can create herd immunity.  And since it might be over a year before such a vaccine is available, we have to be prepared for a lockdown over that entire time of a year or eighteen months.  Or we might try moving back and forth between periods of lockdown and periods of partial opening up of our lives.

This is what is meant by "lowering the curve"--we cannot prevent the COVID-19 virus from killing lots of people, but through locking down our societies, we can reduce the peak death rate by spreading out the deaths over time, while we wait for the vaccine.  As Meyerowitz-Katz says: "The time to discuss herd immunity is when we have a vaccine developed, and not one second earlier."

But notice what this means: we are choosing to prolong the COVID-19 epidemic, instead of allowing the infections to spread quickly enough to achieve herd immunity within two months, because too many people would die during that short time--hundreds of thousands and perhaps even over a million people would die in the U.S. alone.

Notice also that this ignores the fact that a global shutdown bringing a global great depression will destroy the lives of billions of people.  Killing the economy is killing people.

The alternative position is to say that we have a moral obligation to isolate the high-risk group--older people with health problems--and to give them special medical care if they become sick, but we also have a moral obligation to protect human life and liberty from a governmental shutdown of our economic and social life.  That's what we have always done.  Every year, many people die from contagious diseases, but we have never shut down our lives to reduce those deaths.  In 2017, over 60,000 Americans died from the flu epidemic.  In 1918, over 500,000 Americans died from a global flu epidemic.  But there has never been a national shutdown of American society to reduce such deaths in an epidemic.

The epidemiologists who have recommended the shutdown as the only moral response to the COVID-19 pandemic point to the American experience of the 1918 pandemic as proving the wisdom of their recommendation.  Those cities, like St. Louis, where the city government quickly imposed severe measures for social distancing succeeded in reducing the death rates from the flu, while in other cities, like Philadelphia, where the government was slow in imposing such restrictions, the death rates were much higher than they should have been.  Since the COVID-19 virus is as deadly and contagious as the 1918 H1N1 virus, they argue, we must follow policies for mitigating our pandemic similar to those adopted in St. Louis to avoid the mistakes made in Philadelphia.  (See Bootsma and Ferguson 2007; Markel et al. 2007).

I have already written a post on the 1918 flu pandemic in the United States.  Here I want to argue that the history of that pandemic does not support the claim that we must impose a lockdown of our economy as the only reasonable way to handle our present pandemic.

I will make three points.  First, in the 1918 pandemic, those with a high risk of dying from the flu were scattered across the human life span: mortality rates were high for children, for young adults (ages 20 to 40), and for the elderly (over 70).  By contrast, with COVID-19, it's mostly the elderly in poor health who have a high risk of death; and therefore it's possible to reduce the death rate by putting these people in isolation and giving them special medical care when necessary, while leaving children and young adults exposed to infection, so that when herd immunity is achieved, the older people can then be safely returned to their normal social life.

Meyerowitz-Katz contradicts himself on this point.  On the one hand, he says that when herd immunity is achieved, "enough people can't get the disease--either through vaccination or natural immunity--that the people who are vulnerable are protected." On the other hand, he says that with herd immunity achieved by having young people infected, "you'd have clusters of older people with no immunity at all, making it incredibly risky for anyone over a certain age to leave their house lest they get infected, forever."  So which is it--does herd immunity protect the most vulnerable or not?

My second point is that the most harmful policies of today's COVID-19 shutdown--the coercive "shelter in place" orders and the closing down of "nonessential business" for many months--were never adopted by any local or state government in 1918, because political leaders and citizens recognized that this would be too harmful.

On October 6, 1918, the Surgeon General of the United States--Rupert Blue--sent a circular to all the public health departments in the U.S.  He recommended the following five measures for handling the flu epidemic:
"First: That the public be advised of the danger of public assemblies, because of the fact that Spanish influenza is a 'crowd' disease."
"Second:  Impress upon the public that it is the duty of every person to cover his mouth and nose with a handkerchief when sneezing or coughing, because the secretions of the nose and mouth contain the germ of influenza."
"Third:  That upon the appearance of the disease in any town that all theatres, churches, schools, and other places where people assemble be closed until the epidemic has run its course."
"Fourth:  That the people be instructed to remain at home while suffering from a bad cold, as many so-called colds are influenza in a mild form and may develop some serious complications by unnecessary exposure."
"Fifth:  Isolate the patient and allow no visitors to enter the house where a case of influenza may be."
In the days after this message was sent out, many public health officials at both the state and local levels recommended that these policies should be adopted.  In many cities, large public assemblies were banned; theatres, churches, and schools were closed; and people were warned to stay in their homes if they were sick.  In some cities, public health workers went door to door, looking for sick people; and if they found someone sick with the flu, they would put a placard on the home identifying this as a quarantined home.  And yet, most businesses--including restaurants, retail stores, factories, and service and trade occupations--continued to operate.  There was no general lockdown like that imposed now in the U.S. and elsewhere.  (The history of how the 50 largest American cities handled the 1918 epidemic can be found here at a website maintained by the University of Michigan Center for the History of Medicine.)

In Los Angeles, movie houses and theatres were ordered to shut down on October 11, but other businesses that did not create crowded assemblies were open.  The closure order was not lifted until December 2.  On November 7, the Theatre Owners' Association of Los Angeles complained to the City Council that it was not fair to allow so many businesses to remain open.  They argued for closing "all but essential businesses like grocery and drug stores."  There was a prolonged debate over this, but the City Council decided against doing this.

As far as I can tell, St. Louis was the only city where there was a general closure of all "nonessential" stores, businesses, and factories.  In that case, however, this closure lasted for only four days--from November 9 to November 12.  And even so, November 10 was a Sunday, and November 11 was Armistice Day.  So, in reality, this ban shut down the city's economy for only one-and-a-half days.

The first prolonged closure of "nonessential businesses" along with ordering people to "stay home" began on March 19, 2020, with the executive orders issued by the governors of California, New York, and Pennsylvania, which were followed by similar orders from other governors.  In closing down all "nonessential" activity, they were following an advisory memorandum from the U.S. Department of Homeland Security on the "identification of essential critical infrastructure workers during COVID-19 response."  Never before in American history (or in world history!) has anything like this been done, not even in 1918 when the country was faced with the deadliest infectious disease pandemic in human history and one of the bloodiest wars.

My third point against the claim that the experience of the 1918 pandemic shows the need for an economic shutdown to mitigate the COVID-19 pandemic is that some of the American cities with the lowest mortality rates from the flu in 1918 were not severe in their coercive social distancing policies.  A clear example of this was Grand Rapids, Michigan, where out of a population of 138,000, 295 died of the flu in 1918.  Of course, having almost 300 people die of the flue in this one city is disturbing.  But in comparing the flu death rates for 50 large American cities, Grand Rapids had the lowest "excess pneumonia and influenza mortality deaths" per 100,000 population--210.5.  By comparison, Pittsburgh had a flu mortality rate per 100,000 of 806.8.  And St. Louis had a rate of 358.0 (Markel et al. 2007).

In Grand Rapids, there were two very limited closure orders for short periods--lasting a total of 25 days.  The first--lasting 18 days (October 20-November 7)--closed theaters, movie houses, churches, and pool halls; but retail businesses, factories, and schools were open.  The second closure--lasting 7 days (December 17-24)--closed schools, dance halls, skating rinks, lodge halls, and public meeting places; but churches, theaters, retail stores, restaurants, and factories remained open.

The general view in Grand Rapids was that sick individuals should voluntarily isolate themselves at home, but there was no good reason to put healthy people out of work or to deprive people of their public entertainment and church services.  (This looks like the situation in Sweden today.)

And, again, Grand Rapids had the lowest death rates from the flu in 1918.

We can and should end the shutdown.  If we do, we can hope that our death rate from the COVID-19 virus will not be as high as it was for the 1918 virus.  But even if hundreds of thousands of people die from the virus, we will achieve herd immunity--the natural defense against contagious disease--and we will secure our life and liberty.

It is unlikely that the shutdown orders will be lifted anytime soon.  But for as long as those orders are in effect we have the natural right to disobey those orders as tyrannical denials of our natural rights to life, liberty, and the pursuit of happiness.

So, for example, in my state of Michigan, Governor Whitmer by executive order has made it a crime for people to travel to meet with family and friends in their homes.  In effect, she has put the citizens of Michigan under house arrest without due process of law.

Many of us here in Michigan are choosing to violate that order.  On Easter Sunday, many Michigan families will gather in their homes for religious activity and Easter dinner.  Of course, families will be sure to isolate those who might be sick with an infectious illness.  And they will take special care to protect older people from infection.

By order of the Governor, a family gathering like this is criminal behavior.  But we have the natural right to do this.  I hope that there will be many such acts of civil disobedience in Michigan and around the country.


Bootsma, Martin, and Neil Ferguson. 2007. "The Effect of Public Health Measures on the 1918 Influenza Pandemic in U.S. Cities." Proceedings of the National Academy of Sciences 104 (no. 18): 7588-7593.

Fine, Paul, Ken Eames, and David Heymann. 2007. "'Herd Immunity': A Rough Guide." Clinical Infectious Diseases 52 (April): 911-916.

Markel, Howard. 2007. "Nonpharmaceutical Interventions Implemented by U.S. Cities During the 1918-1919 Influenza Pandemic." Journal of the American Medical Association 298: 644-654. Available online.

1 comment:

J. Stack said...

It has been said that it takes time for thought to influence behavior. To what extent do you think the difference in reply to a dangerous flu in 1918 compared to 2020 may be attributed to a widespread acceptance of "comfortable self-preservation" as more important than virtue?