The herd immunity theory is dangerously flawed

The idea of confronting the COVID- 19 pandemic through a strategy of “herd immunity” instead of self- isolation and containment — exposing the population to COVID-19, knowing that most won’t die — seems to have a certain brutal logic. But only until you think about it. Then you see why it could never work in practice. Indeed, it would make things worse.

The idea, in effect, is to bank on the fact that COVID-19 doesn’t kill most people it infects. The death rate is still a matter of some debate, because there are undoubtedly instances of people being infected but not recorded as official cases. But it seems to be in the range of one per cent to perhaps as high as four per cent, with some countries having figures well outside those ranges ( high and low). ( At time of writing, the Canadian fatality rate was just below one per cent of confirmed infections.) The deaths, however, are not evenly distributed among the population. The elderly and those with underlying health conditions are, by far, the most likely to die if infected with COVID-19.

And that’s the core of the herd immunity argument: why not isolate the vulnerable, but allow the rest of us — healthy 30- somethings, such as myself — to get back to work? The 20-, 30- and 40-year-olds will survive, and become immune, and since we’re the heart of the workforce, the economic damage of this crisis would be greatly reduced. Once enough of us are immune, the virus will be vanquished. Right?

No. Wrong. Dangerously wrong. COVID-19 might not kill me, but it can absolutely make me sick — very, very sick. And that’s the piece missing from the herd immunity argument. The health-care system that all of us rely on can break as easily from a surge in sick young patients as doomed elderly ones.

The Centers for Disease Control in the U.S. examined these numbers this week. Counting deaths is important, but counting hospitalizations is also crucial. And this is what breaks the herd immunity argument. Using information available to March 16, and excluding patients where age- related information was not available, the CDC was able to track, by age range, hospitalization rates for a group of more than 2,200 patients. Deaths were absent entirely for those 19 years old and younger; hospitalization in that age group was rare. The age group of 20- 44 year olds, the segment of the population most likely to be healthy and engaged in normal economic activity, though, didn’t fare as well. Among that group, the CDC found that 14.3 to 20.8 per cent required a hospital stay, with two to four per cent requiring life-saving care in an intensive care unit (ICU).

It’s true that very few of these people died. The death rate for the 20- 44 year olds was about 0.1- 0.2 per cent — barely a blip. But they still got very, very sick.

And sickness matters. It matters in economic terms (you aren’t generating much GDP while you’re intubated) but it also matters for the health of everyone. A 40-something COVID-19 survivor who needs a ventilator for five days denies that ventilator to someone else. Every COVID- 19- afflicted young adult in an ICU bed means a bed is not available to someone who might die without it. COVID-19 isn’t the only thing killing people. People are still having heart attacks, discovering tumours and suffering strokes. Accidents are likely down due to the social and economic restrictions, but they haven’t been eliminated. People will still need medical help for as long as this pandemic continues. If someone dies of a heart attack or injury that would otherwise have been survivable for want of an ICU bed occupied by a young COVID-19 victim (who’ll recover), that death won’t be recorded as COVID- related, but it absolutely is.

We’ll probably eventually have a sense of how many such deaths we are going to see during this pandemic. There’ll be statistical data accumulated in the next six weeks that will take decades to properly analyze. But we’re already seeing some anecdotal signs of these secondary pandemic deaths. On Thursday, the AFP news agency reported that even as COVID-19 is killing Italians by the thousands, local death rates in highly afflicted areas are showing surges well above expected seasonal levels that cannot be accounted for by COVID-19 alone. In the town of Bergamo, the AFP reported, the local public health officer and the mayor could not reconcile the figure for COVID-19 deaths, which stood at 31, with the devastation in their community. So they looked at total deaths, and found that since Jan. 1, 158 people have died in that town. Last year, the number of total deaths was 35. That’s 123 “extra” deaths, of which COVID-19 claimed a quarter. What about the rest?

Some of the gap might be explained by reporting glitches or misdiagnoses, but it’s near certain that some of those extra deaths are people who would have lived had the local health- care system not been overwhelmed by COVID-19.

That’s the problem with the herd immunity argument. COVID- 19 doesn’t produce simple binary outcomes — dead or not dead — but a much more serious and nuanced impact across almost all age groups in the population. Some die, some never have any symptoms, and the rest become ill to some extent — and that extent ranges from mild symptoms to life-threatening respiratory distress. Across the world, health- care systems operate with virtually no excess capacity; I recently asked an emergency room doctor at a major Toronto hospital how many spare ICU beds his large facility had on any given shift. He looked at me, baffled, and said, “Zero,” as if it was a stupid question. And you know what? It was. The overcrowding of our hospitals is old news.

Thousands of sick young people can crash a healthcare system as effectively as thousands of dying seniors. And then more people will die total: the COVID-19 death rate would soar dramatically if health- care systems collapsed. Again, this has happened in Italy, which has a fatality rate of almost 10 per cent. Perhaps there are some environmental or regional factors at play there, but it’s more likely that the sky-high death rate is explained by a health- care system that’s simply too overburdened to save the marginal cases of all types, not just COVID-19.

And that’s the second problem with the notion of restarting the economy by banking on herd immunity. Bluntly, no politician would dare see it through. The British government considered it; U. S. President Donald Trump is still openly musing about trying to reopen America for business in a few weeks. It’s simply inconceivable that any politician in the world today would stick to this plan as ICU wards filled up with young people gasping for breath and hoping for a ventilator.

Even China, a brutal authoritarian regime that never hesitates to victimize its own people, put down the hammer on its own economy rather than let the virus spread. Do we think we’d somehow be tougher than the Chinese Communist Party? No Western politician would actually stick with a herd immunity plan, and they’d end up infecting many more of their citizens than need be afflicted before their nerve eventually broke. That longer, larger epidemic would obviously result in yet more economic damage.

Eventually, the herd will be immune — enough of us will be infected, or eventually vaccinated, to contain COVID-19. The economic damage during that period will be gigantic — beyond our comprehension. But it’s the least-bad option. No matter your age, your life may depend on sticking with the isolation plan. It’s bad. But it can be worse.