Herd immunity’s a great strategy, if you don’t mind the millions of dead

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As the second wave of the coronavirus pandemic washes over Europe and Canada, the United States is already into its third. The number of new cases, which had fallen to less than 36,000 a day as recently as last month, has surged to more than 50,000; forecasts suggest it will crest to 150,000 by the end of the year. The number of new deaths due to the virus, now at roughly 700 a day, is likewise projected to triple, with no guarantees there will not be a fourth peak after that, and a fifth after that.

Relax, it’s all part of the plan. You thought the U.S. outbreak of COVID-19, among the very worst in the world, was the disastrous but predictable result of a president, and an administration, that failed to take the disease seriously until it was too late; that has yet to assemble a coherent plan to fight it, even as it mocks and impedes the efforts of state and local governments; that has peddled a variety of false cures even as it pretends the disease will disappear on its own? No, no, no, it’s not like that at all.

No, the virtually uncontrolled spread of the virus in the United States, infecting more than eight million Americans to date and killing about 220,000 of them, would seem to have been a matter of deliberate strategy – by the White House’s own account. Based on the concept of “herd immunity,” or as it is now being called, “focused protection,” the idea was briefly in circulation six months ago, when very little was known about the virus or how to contain it, but has since resurfaced in the form of the grandly named Great Barrington Declaration.

The brainchild of three epidemiologists, it was posted online earlier this month, where it has attracted the signatures of nearly 10,000 “medical and public health scientists.” Lately it has been taken up by the Trump administration. After meeting with the three last week, Health and Human Services Secretary Alex Azar tweeted that their proposal provided “strong reinforcement of the Trump Administration’s strategy.” A senior administration official embraced it as an endorsement of “what the President’s policy has been for months.”

The idea has been likened to a “national chicken pox party.”

Far from limiting the spread of the disease, the proposal is to actively propagate it, at least among the young and healthy. Rather than wear masks and keep their distance from each other, still less avoid public gatherings, people would be encouraged to go about their business as usual, until herd immunity was reached: the point at which enough of the population has been infected, and is presumably immune, that the disease begins to die out for lack of new carriers. Protective measures would apply only to the old and the infirm, for whom the disease is much more deadly.

There’s nothing wrong with herd immunity, as a concept. It is, after all, the basis of mass immunization programs. But this would be the first attempt in world history to use the disease itself – a disease that has already killed more than a million people around the world – as the vaccine. Possibly there is a reason for this. In fact there are several.

First, the U.S. is nowhere near to herd immunity. (Canada, with a fifth as many cases per capita, is even further.) Even at eight million-plus, the number of confirmed cases to date amounts to less than 2.5 per cent of the population. Of course many more are likely to have been infected than the official count, but even if the real number were four times as high – in line with evidence from population blood samples – it would still be less than 10 per cent.

The level required for herd immunity is the subject of some conjecture. It is normally calculated based on the virus’s basic “reproduction number,” the famous R0: the number of people each carrier infects, on average, or would if no preventive measures were in place. At an R0 of three, you’d need to infect at least two-thirds of the population to reach herd immunity. At an R0 of four, the threshold for herd immunity would be 75 per cent; at two, 50 per cent; and so on.

Suppose the actual proportion were 60 per cent, the bottom end of most estimates. That means an additional 50 per cent of the population would have to be infected, on top of those who have been infected to date.

Even at the current U.S. death rate of about 1.4 per cent of confirmed cases – much reduced from the spring – that means another 500,000 dead, minimum. At the overall “case fatality ratio” of 2.7 per cent, the number of additional deaths would be more like 1.1 million. All of the suffering, all of the dead, all of the grief and pain and loss Americans have endured thus far, times five.

Question: How fast are you going to infect people, assuming you can control such a thing? Part of the reason death rates were so much higher in the spring was the arrival of so many cases at the same time in hospitals that were already stretched to the limit. It took six months to infect the first 10 per cent of the population. Do you infect the other 50 per cent in the same time frame? Then look for vastly more overloaded hospitals, and vastly higher death rates.

But if you try to slow the infection rate – hey, maybe we should tell people to wear masks! – you run into a more purposeful objection. A vaccine is on the way, probably within six months, almost certainly within a year. What would be achieved by “natural” herd immunity that could not be achieved, as soon or sooner, by the vaccinated kind – without the millions of sick and dead?

There are many other objections to the “herd immunity” strategy. Getting the disease is no walk in the park, even for young people; if it doesn’t kill you, it can still have serious, and lasting, effects. Isolating the elderly from the rest of the population, likewise, is not so easy as it sounds.

Neither is the immunity conferred by infection permanent, or even certain: In most, it lasts a few months. So you infect all those tens of millions of people, and for what? So they can become infected all over again, and infect others, as soon as next spring.

The only permanently immune are the dead. Maybe next the White House will tell us that’s the plan.

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