The Pandemic’s Future: A Book Review on ‘From Killer to Common Cold’
By: Bo Stapler
Tags: Covid-19, Science, Healthcare, Coronavirus, Health

Coronavirus

The Pandemic’s Future: A Book Review on ‘From Killer to Common Cold’

This book describes the concept of herd protection, which is different from herd immunity, and how the remainder of the pandemic will unfold.

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The explosion of scientific literature on Covid-19 and its extensive coverage from mainstream and other media sources has resulted in a downpour of fresh details about the virus. Hardly a day goes by without some new finding of a previously unrecognized symptom, an observational study on a repurposed drug, an argument about masks, the story of a country that finally got it right or, perhaps, one that keeps getting it wrong. What’s important and what’s not? Sometimes it seems impossible to see the forest for the trees.

Many individuals, particularly those in the United States, are still searching for a trustworthy and comprehensive guide to navigating the pandemic, and I believe this book, “From Killer to Common Cold” delivers.

Its author, David Graham, MD, a board-certified infectious disease specialist, needs just 78 pages to answer the most relevant and fundamental questions many are asking about the novel coronavirus like, ‘What will the pandemic look like moving forward?’ and ‘How do we reasonably protect ourselves and loved ones?’

Graham takes a unique approach by personifying the virus and identifying its ‘goals’ from an evolutionary perspective. Rather than clinging to every piece of pre-published minutiae — a mistake some experts, myself included, have made — Graham uses his unique understanding of coronaviruses, both past and present, he has accumulated while practicing infectious disease. He wraps his extensive knowledge into a neat package and succinctly delivers it to his readers. So, let’s take a brief look at what this book is about.

That is because Graham, along with many other health experts, recognized early on that SARS-CoV-2 had spread too far and was too difficult to trace that it could no longer be eradicated.

The end result is not in question

In the first chapter, Graham asserts that the ultimate outcome of the pandemic is clear. The part of the pandemic that remains in question is what happens between now and the end. He comments, “I believe the destiny of [the virus] SARS-CoV-2 is already written. With or without a vaccine, with or without an effective treatment, with or without expected technological advances, we are destined to interact with this virus forever.”

Graham notes that there are four other coronaviruses, namely HCoV-229E, -NL63, -OC43, and -HKU1, that have caused epidemics or pandemics in the past. These viruses were likely more deadly to humans initially but now cause the common cold. Their progression to a less lethal version of themselves is a product of evolutionary biology. Just as with the novel coronavirus, these previous coronaviruses likely caused symptoms that ranged from nothing, to that of a common cold, to pneumonia and even death.

Our ancestors who survived previous coronavirus pandemics, at least the ones of childbearing age or younger, possessed immune systems capable of withstanding the virus. In the past, as well as today, immunity to these older coronaviruses would wane over time. However, as we’ve seen with Covid-19, patients who overcome initial infections generally retain enough immunity to survive subsequent exposures and infections as well.

According to Graham, the common-cold coronaviruses have become endemic meaning they, “circulate widely, at all times, and in low levels in human populations throughout the world.” He foresees that “SARS-CoV-2 will become the fifth endemic human coronavirus.” That is because Graham, along with many other health experts, recognized early on that SARS-CoV-2 had spread too far and was too difficult to trace that it could no longer be eradicated.

In contrast, the two other known coronaviruses, SARS and MERS, that caused outbreaks earlier this century failed to become endemic, each for a slightly different reason. SARS was too lethal and didn’t have a long incubation period. As a result, cases of SARS could be traced until it was eliminated from the human population. MERS, which is endemic among camels, is transmitted poorly from human to human. So, despite MERS also being very lethal, it has not spread significantly within the human population.

No, herd protection is not Graham’s attempt at a more socially acceptable definition of herd immunity.

What is herd protection?

After establishing that SARS-CoV-2 will become endemic with an ever-declining lethality, Graham moves on to discuss how this will take place. He starts by coining and describing the term ‘herd protection’. No, herd protection is not Graham’s attempt at a more socially acceptable definition of herd immunity. It is a unique concept that, in my opinion, cleverly bridges the gap between increasingly divergent schools of thought regarding herd immunity. But before we get to herd protection, let’s back up and review the definition of herd immunity.

If you recall, the concept of herd immunity can be defined as the minimum percentage of a population needed to be immune to a disease in order for the disease not to transmit efficiently. This percentage is determined by how contagious a disease is. Most epidemiologists project the threshold for herd immunity to Covid-19 to be about 60–80% of the population. So, when 60–80% are immune, the pandemic starts slowing. It doesn’t fully halt, though, in part because immunity to Covid-19 isn’t permanent. The virus in this scenario then becomes endemic and continues to circulate causing fewer infections and less deadly outbreaks as the years go on.

Graham explains that herd immunity is not an ideal term to use when referring to Covid-19. He believes the label of herd immunity should generally be reserved for diseases that can be stopped through vaccination alone. While a vaccine may be helpful to some degree for Covid-19, the end of the pandemic will occur by way of a number of factors, not just a vaccine. These factors form the components of herd protection and include, heterogeneous mixing, pre-existing immunity, absence of susceptibility, naturally acquired immunity, and immunity acquired by vaccination. We’ll breakdown what each of these means in a moment.

I realize it might sound like splitting hairs over semantics, but I can’t emphasize enough the importance of this concept, herd protection. There is considerable debate about whether natural herd immunity to Covid-19 is possible, if it would be good for society, and if it should be a strategy to manage the pandemic. Undertones of this dispute arise from scientific publications to social media posts and everywhere in-between.

Graham neutralizes this issue by revealing that herd protection is indeed possible, it’s how the pandemic will end, and its arrival is unequivocally good for society. Herd protection is not a strategy, per se, but it’s a goal. It provides a target that governments, communities, and their leaders can aim for. The goal isn’t to get there as quickly as possible, but to arrive safely and minimize suffering along the way.

Now, let’s unpack each of the components of herd protection and how they contribute to the immunity of a population.

1. Heterogeneous mixing

Calculations for herd immunity traditionally assume a population that mixes randomly. Graham recognizes, however, that, “We don’t mix randomly, but rather with the same people over and over again. And some mix more than others.” This lack of random mixing is called heterogeneous mixing. Although this is probably the most esoteric component of herd protection, it’s important to mention nonetheless. Okay, let’s move on to the others.

2. Pre-existing immunity

By using the term, pre-existing immunity, Graham is referring to a subset of people who have been exposed to other coronaviruses in the past besides SARS-CoV-2. The immune systems of some of these individuals are able to recognize and attack the novel coronavirus in addition to whatever other coronaviruses they were exposed to previously. This is called cross-reactivity, and some researchers estimate that the immune systems of 40–60% of the population may possess cross-reactivity to SARS-CoV-2. Science author, Dr. Dana Smith explains the concept very articulately here:

3. Absence of susceptibility

Another phenomenon Graham highlights is the idea that some individuals are susceptible to infection from SARS-CoV-2 while others are not. He considers outbreaks on cruise ships or in prisons and wonders, “Why don’t 100% of people get Covid-19 after significant exposure?” This is not the same thing as pre-existing immunity and may be related to genetic predisposition.

Graham uses the example of rare individuals who lack the cellular receptors used by HIV to enter cells. These people don’t get HIV because it literally can’t enter their bodies. It’s not that they’re immune, they just aren’t susceptible. Similarly, and for reasons that remain unclear, there are a number of people who aren’t susceptible to Covid-19. Research indicates that this number is higher for younger people. Graham uses figures derived from an article published in the journal, Nature Medicine, below, to describe the concept.